AU2002361217A1 - Highly sensitive and continuous protein-tyrosine-phosphatase (PTPase) test using 6,8 difluoro-4-methyl-umbelliferylphosphate - Google Patents

Description

WO 03/056029 PCT/EPO2/14755 Description A highly sensitive and continuous protein tyrosine phosphatase (PTPase) test using 6,8-difluoro-4-methylumbelliferyl phosphate. 5 The invention relates to an improved method for detecting protein tyrosine phosphatases, in particular under neutral conditions, using 6,8-difluoro-4 methylumbelliferyl phosphate. 10 The prior art discloses methods for detecting the activity of a protein tyrosine phosphatase using the substrate p-nitrophenyl phosphate (p-NPP). These detection methods are to be found in standard biochemical manuals such as "Current protocols in protein science: John E. Coligan (ed.), Ben M. Dunn (ed.), Hidde L. Ploegh (ed.), David W. Speicher (ed.), Paul T. Wingfield (ed.); SBN: 0-471-11184-8; 15 loose-leaf pages, continuously updated; published by John Wiley & Sons." The action of a phosphatase forms p-nitrophenol from the p-NPP. P-Nitrophenol can be detected photometrically on the basis of its intense yellow color in the alkaline range. However, this test method has some unfavorable features. The test is not suitable for 20 directly determining the activity of the enzyme since it is carried out in accordance with the time-stop principle. In accordance with this principle, the enzyme reaction is interrupted by adding sodium hydroxide solution after a given period of time has elapsed. The increase in the pH leads to the color of the resulting p-nitrophenol changing to yellow, the absorption of which is determined photometrically and is a 25 measure of the quantity of p-nitrophenol which is present. This test principle is rather elaborate for enzyme-kinetic investigations, for example for determining the type of inhibition. Since a large number of experimental points are required, a corresponding number of individual assays, which are coordinated with each other, have to be set up. 30 In addition, the substrate is sensitive to light, temperature and pH. In the physiological pH range, it has a tendency to decompose slowly.

2 When pNPP is used as the substrate, some of the tyrosine phosphatases to be investigated have an activity maximum which is in the acid range. For example, PTP1B shows a greater turnover at a pH of 5.6. On the other hand, at the physiological pH of 7.0, PTPI1B is only operating at 30% of the maximum turnover 5 value when using pNPP as substrate. This makes it necessary to use relatively high quantities of the enzyme, resulting in a corresponding increase in costs. Another negative factor of this test method is that other components which are present in the test, such as buffers, salts or other substances (test substances), from time to time absorb in the yellow range. This requires appropriate background controls. 10 The malachite green phosphopeptide test has been described as another method for detecting the activity of protein tyrosine phosphatases (Martin et al. (1985) Journal of Biological Chemistry, 260, pp. 14932 and Harder et al. (1994) Biochemical Journal, 298, pp. 395). In this method, the inorganic phosphate which the phosphatase has 15 released from its substrate peptide is detected photometrically using the malachite green reagent. Apart from the temperamental nature of the photometric determination, resulting, for example, from impurities or pH sensitivity, and the laboriousness of the time-stop method, another disadvantage is that the specific substrate peptide has to be prepared in high concentration for each phosphatase, 20 something which generally makes the method rather expensive. 3,6-Fluorescein diphosphate has been described as being another substrate for detecting protein tyrosine phosphatases (Journal of Biomolecular Screening 4, 327 334, 1999). While this substrate, in contrast to the two substrates mentioned above, 25 enables the enzyme activity to be measured directly, the spectral properties of this substrate are still not particularly good for carrying out measurements in the physiological pH range. The object of the present invention is therefore to make available another 30 The invention relates to a method for detecting the enzymic activity of a protein tyrosine phosphatase in biological material, which comprises a] providing biological material or a preparation obtained from biological material, b] providing 6,8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), 3 c] bringing the biological material or the preparation obtained from biological material from a] into contact with the DiFMUP from b] in an aqueous solution, 5 d] fluorometrically detecting the 6,8-difluoro-4-methylumbelliferyl which is then formed. The preparation obtained from the biological material preferably comprises a protein tyrosine phosphatase from the group LAR, CD 45, PTP alpha, PTP 1B, TCPTP, 10 YOP, CDC 25, PTEN and SHP1,2. The preparation obtained from the biological material can be present in different stages of purity. The preparation obtained from the biological material can be whole cells, disintegrated cells, samples enriched with cell components and/or organelles, or purified proteins. 15 When being brought into contact with the biological material or the preparation obtained from biological material, the concentration of the 6,8-difluoro-4 methylumbelliferyl phosphate (DiFMUP) is preferably from 10 to 250 pM. Particularly preferably, the concentration of the DiFMUP is from 50 to 100 pM. 20 The pH of the aqueous solution in which the biological material or the preparation obtained from biological material is brought into contact with the DiFMUP is preferably between 5.0 and 8.0 and particularly preferably between 6.0 and 7.5. In an embodiment which is once again particularly preferred, this pH is 7.0. 25 The invention also relates to a method for identifying a compound which modifies the activity of a protein tyrosine phosphatase, which comprises a] providing a chemical compound, b] providing biological material or a preparation obtained from biological material, 30 c] providing 6,8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), d] bringing the chemical compound from a] and the biological material or the preparation obtained from biological material from b] and the DiFMUP from c] into contact with each other in an aqueous solution, 4 e] determining fluorometrically the quantity of the 6,8-difluoro-4 methylumbelliferyl which is then formed, f] comparing the quantity, from e], of 6,8-difluoro-4-methylumbelliferyl which is formed with the quantity of 6,8-difluoro-4-methylumbelliferyl which is formed in 5 a control assay. A control assay is characterized, in particular, by the fact that, when the biological material or the preparation obtained from biological material is brought into contact with DiFMUP, either no chemical compound is involved in the sense of the previously mentioned procedural step a) or the effect of the chemical compound in 10 relation to a protein tyrosine phosphatase of the chosen type is already known. Such chemical compounds, which are used in the control assay and whose effect on a protein tyrosine phosphatase is already known, can, in particular, be vanadate, vanadium organic compounds, pervanadate, okadaic acid, NaF, dephostasin, modified peptides or other compounds. 15 In various preferred embodiments of the method for identifying a compound which modifies the activity of a protein tyrosine phosphatase, this modification should comprise a stimulation, inhibition or stabilization of the activity of a protein tyrosine phosphatase. 20 In another preferred embodiment of the method for identifying a compound which modifies the activity of a protein tyrosine phosphatase, this protein tyrosine phosphatase is selected from the group comprising the group LAR, CD 45, PTP alpha, TC-PTP, CDC 25, PTEN, YOP, SHP1,2. and PTP1B. 25 The invention also relates to a compound which modifies the activity of a protein tyrosine phosphatase and which has been identified by the above-described method for identifying a compound which modifies the activity of a protein tyrosine phosphatase. This compound preferably has a mass of between 0.1 and 50 kDa, 30 additionally preferably of between 0.1 and 5 kDa and additionally preferably of between 0.1 and 3 kDa. The compound can be a protein, an amino acid, a polynucleotide, a nucleotide, a natural product or an aromatic hydrocarbon compound. The invention also relates to a pharmaceutical which comprises at least one compound as described above, which compound has been identified by a 5 method for identifying a compound which modifies the activity of a protein tyrosine phosphatase. The pharmaceutical additionally comprises auxiliary substances for formulating a pharmaceutical and/or polymeric additives. 5 The invention also relates to the use of a compound, which has been identified by a method for identifying a compound which modifies the activity of a protein tyrosine phosphatase, for producing a pharmaceutical for treating diabetes. 6,8-Difluoro-4-methylumbelliferyl phosphatase is commercially available. For 10 example, the company Molecular Probes Europe BV (2333 Leiden, The Netherlands) markets this chemical. Its preparation is disclosed in US 5,830,912. Biological material is any material which contains genetic information and itself also bacteria or fungi such as Escherichia coli or Saccharomyces cerevisiae. Biological 15 material also comprises cells from cell cultures. In the case of cells from animal or human tissues, biological material can be obtained by biopsy, surgical removal or removal using syringes or catheters, or comparable techniques. The cells which have been removed in this way can be 20 deep-frozen, worked up or taken into culture. Bacteria and yeast cells are propagated using customary microbiological techniques and worked up. The skilled person will find appropriate instructions for this purpose in "Current Protocols in Molecular Biology; ed.: F.M. Ansabel et al., loose-leaf publication, 25 continuously updated, 2001 edition, published by John Wiley & Sons". Biological material can also comprise the cells from a culture of animal cells. Examples of such cells are mouse cells, rat cells or hamster cells. The cell culture cells can be primary cell types or established cell lines. Examples of established cell lines are mouse 3T3 cells, CHO cells or Hela cells. The maintenance, growth and 30 propagation of cell lines is described in standard textbooks, for example in "Basic Cell Culture; ed.: J.M. Daris IRL Press, Oxford (1996)". A preparation obtained from a biological material is prepared, for example, by the disruption of the biological material and by subsequent purification steps. Methods for disrupting the biological material can be, in particular, repeated freezing and 6 thawing, sonication, the use of a French press or the addition of detergents and enzymes, or the like. Subsequent purification steps comprise, for example, differential centrifugation, precipitation with ammonium sulfate or organic solvents, the use of chromatographic techniques, etc. Examples of chromatographic 5 techniques are polyacrylamide gel electrophoresis, high pressure liquid chromatography, ion exchange chromatography, affinity chromatography, gas chromatography, mass spectrometry, etc. Textbooks, such as, in particular, "Current Protocols in Protein Science, ed.: J. E. Coligan et al., loose-leaf publication, continuously updated, 2001 edition, published by John Wiley & Sons" are available 0 to the skilled person for this purpose and, in particular, also for detailed instructions with regard to purifying proteins. The biological material or the preparation obtained from biological material can be brought into contact with DiFMUP in customary laboratory vessels such as 5 Eppendorf tubes, centrifuge tubes or glass flasks. The underlying aqueous medium contains, for example, buffering substances, nutrient medium constituents, singly charged or doubly charged ions, such as Na , K , Ca 2+ , Cl, SO 4 2 and P0 3 2- , or other ions, and, in addition, proteins, glycerol or another substance. For the bringing-into contact, specific constant conditions, such as, in particular, the temperature, the pH, 0 the ionic conditions, the concentration of a protein, the volume, or other factors, can be advantageous. This is achieved by, for example, carrying out the bringing-into contact in incubation devices which are kept at a constant temperature, in the presence of a buffer or using quantities of the ions or proteins which have previously been weighed out accurately. The aqueous solvent can, in particular, also contain a 5 particular proportion of an organic solvent, such as dimethyl sulfoxide, methanol or ethanol. However, the content of such a solvent is preferably not more than 10% by volume of the mixture. The PTPase (phosphatase) protein family currently comprises about 100 different 0 members. These members can be roughly subdivided into receptor-coupled proteins and cytoplasmic proteins. The phosphatases possess in common the amino acid motif (HN)CX 5 R(S/T) in the catalytic domain. The receptor-coupled phosphatases are usually composed of an extracellular domain, a single transmembrane region and one or two cytoplasmic PTPase domains. The LAR (leukocyte common antigen- 7 related) protein and the PTPa proteins are considered to belong to the receptor coupled PTPases. The intracellular PTPases normally contain a catalytic domain and various extensions of the C-terminal or N-terminal region, for example as a result of "SH domains". These extensions are ascribed functions in targeting or 5 regulation. The enzyme PTP1B is assigned to the cytoplasmic PTPases. In addition to the pure tyrosine phosphatases, the PTPase family also includes the group of dual phosphatases. In addition to phosphotyrosine, these enzymes also use phosphoserine or phosphothreonine as the substrate. This group includes, for example, the phosphatases VHR and cdc25. 0 The phosphatases LAR, PTPa, SHP-2 and PTP1B are ascribed important functions in the insulin-mediated signal pathway. These PTPases associate with the insulin receptor and catalyze the dephosphorylation. These PTPases may possibly play a role, individually or in combination, in the pathogenesis of insulin resistance 5 (Biochemistry 38, 3793-3803, 1999; p. 3799). PTP1B is a negative regulator of the insulin-stimulated signal transduction pathway, i.e. the protein once again switches off the signal which was induced by insulin. Presumably, the signal pathway is interrupted by the insulin receptor being directly .0 dephosphorylated. PTP1B is also overexpressed in a large percentage of patients suffering from breast cancer. In addition, the enzyme interacts with the "epidermal growth factor". The enzyme has been demonstrated to possess two aryl phosphate binding pockets. One is located directly in the active center while another is located outside of this at a site which is adjacent to the catalytic center. .5 (Biochemistry 38, 3793-3803, 1999). The transmission and termination of many intracellular signals is controlled by the tyrosine-phosphorylation of the factors involved. A precisely balanced activity of complementary protein tyrosine kinases (PTKs) and phosphatases (PTPases), in 0 particular protein tyrosine phosphatases, establishes the phosphorylation state. As enzymes, PTPases are responsible for selectively dephosphorylating phospho tyrosine residues. PTPases function, in interplay with the protein tyrosine kinases, in a great variety of different biological processes, in mediating signals due, for 8 example, to growth factors or hormones. These signal transduction mechanisms play an important role in regulating cell metabolism, growth, differentiation or mobility. The faulty regulation of signal pathways is thought to be one of the causes of a 5 number of pathological processes. These processes include, for example, cancer, some immunological and neurological diseases, and also type II diabetes and obesity. A chemical compound is provided, for example, by means of chemical synthesis. 0 The skilled person is familiar with the standard methods of synthesis. The chemical compound can be part of a collection of chemical compounds, as are formed by storing and cataloging the chemical compounds from synthesis programs which have been concluded (what are termed chemical libraries). In other cases, the compound can have been formed by a microorganism, in particular a bacterium, or 5 else by a fungus or a plant (natural product). Suitable pharmaceutical compounds for oral administration can be present in separate units, such as capsules, cachets, sucking tablets or tablets, as powders or granules, as a solution or a suspension in an aqueous or non-aqueous liquid, or as .0 an oil-in-water or water-in-oil emulsion. These compositions can be prepared in accordance with any suitable pharmaceutical method which comprises a step in which the active compound and the excipient (which can be composed of one or more additional constituents) are brought into contact. In general, the compositions are prepared by uniformly and homogeneously mixing the active compound with a !5 liquid and/or finely divided solid excipient, after which the product is formed, if required. Thus, a tablet can be prepared, for example, by pressing or forming a powder or granulate of a compound, where appropriate together with one or more additional constituents. 10 Pressed tablets can be prepared by tableting the compound in freely flowing form, such as a powder or granulate, where appropriate mixed with a binder, a glidant, an inert diluent and/or a (several) surface-active/dispersing agent(s), in a suitable 9 machine. Formed tablets can be prepared by forming the pulverulent compound, which has been moistened with an inert liquid diluent, in a suitable machine. Pharmaceutical compositions which are suitable for peroral (sublingual) 5 administration comprise sucking tablets which contain a compound together with a flavoring substance, customarily sucrose and gum arabic or tragacanth, and lozenges, which comprise a compound in an inert base such as gelatin and glycerol or sucrose and gum arabic. O Suitable pharmaceutical compositions for parenteral administration preferably comprise sterile aqueous preparations of a compound, which preparations are preferably isotonic with the blood of the intended recipient. These preparations are preferably administered intravenously, even if the administration can also take place subcutaneously, intramuscularly or intradermally as an injection. These preparations 5 can preferably be produced by mixing the compound with water and making the resulting solution sterile and isotonic with blood. Injectable compositions according to the invention generally comprise from 0,.1 to 5% by weight of an active compound. Suitable pharmaceutical compositions for rectal administration are preferably present 0 in the form of single-dose suppositories. These can be produced by mixing a compound with one or more conventional solid excipients, for example cocoa butter, and forming the resulting mixture. 5 Suitable pharmaceutical compositions for topical use on the skin are preferably present in the form of an ointment, cream, lotion, paste, spray, aerosol or oil. Excipients which can be used are Vaseline, lanolin, polyethylene glycols, alcohols and combinations of two or more of these substances. The active compound is generally present at a concentration of from 0.1 to 15% by weight of the composition, 0 for example of from 0.5 to 2%. A transdermal administration is also possible. Suitable pharmaceutical compositions for transdermal uses can be present as individual plasters which are suitable for close, long-term contact with the epidermis of the patient. Such plasters suitably 10 comprise the active compound in an aqueous solution which is buffered, where appropriate, dissolved and/or dispersed in an adhesive or dispersed in a polymer. A suitable active compound concentration is from approx. 1% to 35%, preferably from approx. 3% to 15%. 5 Type 2 diabetes (NIDDM - non-insulin-dependent diabetes mellitus) is characterized by high glucose values (hyperglycemia) in the fasting state (> 126mg/dl), insulin resistance in peripheral tissues such as muscle or fat, an increase in gluconeogenesis in the liver and inadequate secretion of insulin by the pancreatic f 0 cells. The actual cause of this disease is still not known. Type 2 diabetes very frequently occurs together with other clinical pictures, such as obesity, hypertriglyceridemia (elevated blood fat values) and high blood pressure. Insulin resistance is suspected to be a key to understanding the clinical picture. 5 Insulin resistance is expressed in a decreased ability of the peripheral organs to react to a defined concentration of insulin. This is reflected at the cellular level, i.e. in an increase in the quantity of insulin which is required for inducing an effect due to insulin. In muscle, fat and liver cells, insulin has a variety of effects on glucose metabolism and fat metabolism, such as increasing the uptake of glucose from the ?0 blood, increasing the rate at which glucose is metabolized or inhibiting fatty acid cleavage. A variety of factors are thought to have a fundamental connection with the development of insulin resistance at the cellular level. The insulin receptor, the factors of the signal cascade, and the components of the glucose transport system, play an important role in this context. .5 Insulin brings about its biological functions by, in the first step, binding to the insulin receptor. After this receptor has bound the insulin, its f subunit is subjected to autophosphorylation by the insulin receptor kinase. In muscle cells, the signal is cellularly transmitted by way of the IRS (insulin receptor substrate) and PI3K 0 (phosphoinositol-3-kinase) and leads to glucose uptake being stimulated. Insulin brings about a large number of other effects which proceed by way of mechanisms which are only partially understood. In the intracellular transmission of the signal, specific kinases and phosphatases act together in a coordinated manner. Dissociation of the insulin from the receptor is not sufficient to switch off the signal 11 induced by the insulin. The tyrosine kinase activity of the insulin receptor persists as long as the regulatory domain remains phosphorylated. Cellular PTPases are responsible for switching off the signal. Pharmacologically active compounds which have an inhibitory effect on negative regulators of the insulin signal pathway have 5 the potential to delay dephosphorylation of the insulin receptor. This provides the possibility of being able to use the substances for decreasing the resistance to insulin. Abbreviations 10 LAR leucocyte antigen-related protein tyrosine phosphatase CD 45 leucocyte phosphatase CD 45 YOP yersinia protein tyrosine phosphatase 5 PTP alpha protein tyrosine phosphatase alpha PTP 1B protein tyrosine phosphatase 1B TC-PTP T cell - protein tyrosine phosphatase CDC-25 cell-division-control phosphatase 25 PTEN phosphatase (dual specific) within chromosome 10 _0 SHP 1,2 src-homology phosphatase 1,2 Examples: 1. Cleavage of DiFMUP in dependence on the concentration of the PTP1B enzyme: ?5 The reaction takes place in a black microtiter plate at a temperature of 37 0 C. 135 p/1l of reaction buffer are provided per enzyme concentration to be analyzed, with this reaction buffer containing the following components: protein tyrosine phosphatase PTP1B at the desired final concentration (Figure 1: 30 - 600 ng/ ml); 50 mM Hepes, 10 pH 6.9; 150 mM NaCI; 1 mM EDTA; 2 mM DTT. The phosphatase reaction is started by adding 15 p1l of 1 mM DiFMUP solution and the increase in fluorescence (measured in RFU) is measured, continuously for 15 minutes, in a fluorescence microtiter plate photometer at an excitation wavelength of 358 nm and an emission wavelength of 455 nm. The measure of the enzyme activity is the increase in 12 fluorescence in dependence on the final concentration of PTP1B, which can be depicted graphically (Fig. 1). 2. Concentration dependence of the cleavage of DiFMUP by PTP1B. 5 The reaction takes place in a black microtiter plate at a temperature of 370C. 135 p1 of reaction buffer are provided in each case, with this buffer containing the following components: 100 ng of protein tyrosine phosphatase PTP1b/ml; 50 mM Hepes, pH 6.9; 150 mM NaCI; 1 mM EDTA; 2 mM DTT. The phosphatase reaction is started by 0 adding 15 p1 of DiFMUP solution, which contains the substrate at 10 times the final concentration which is desired in the test mixture (Figure 2: 0 - 200 pM), and the fluorescence is measured, at time intervals of 30 seconds for a period of 15 minutes, in a fluorescence microtiter plate photometer at 358 / 455 nm. The measure of the enzyme activity is the increase in fluorescence (measured in RFU) in dependence on 5 the DiFMUP concentration, which can be depicted graphically (Fig. 2). This graph can subsequently be used to determine the kinetic constants of the enzyme reaction by means of a Lineweaver-Burk analysis. Thus, PTP1B is found to have a Km value of 19 pM and a Vmax of 388000 RFU sec -1 ' mg- 1 . This analysis can also be carried out in an analogous manner for other tyrosine phosphatases. The kinetic constants 0 are given in Table 1. 3. Cleavage of DiFMUP in dependence on the concentration of the phosphotyrosine phosphatase enzymes PTPalpha, LAR, T cell-PTP, SHP-2, CD45 and YOP. 5 The reaction takes place in a black microtiter plate at a temperature of 37 0 C. 135 p1 of reaction buffer are provided per enzyme and per enzyme concentration to be analyzed, with this buffer containing the following components: protein tyrosine phosphatase at the desired final concentration (Fig. 3: PTPalpha: 0.5 - 1.85 pg/ ml, 0 LAR: 125 - 500 ng/ ml; Tcell-PTP: 66 - 330 ng/ ml; CD 45: 50 - 400 ng/ ml; YOP: 50- 400 ng/ ml; SHP-2: 0.3 - 2.4 pg/ ml); 50 mM Hepes, pH 6.9; 150 mM NaCl; 1 mM EDTA; 2 mM DTT. The phosphatase reaction is started by adding 15 p/1 of 1 mM DiFMUP solution and the fluorescence is measured, at time intervals of 30 seconds and over a period of 15 minutes, in a fluorescence microtiter plate 13 photometer at 358 / 455 nm. The measure of the enzyme activity is the increase in fluorescence (measured in RFU) in dependence on the final concentrations of the protein tyrosine phosphatases, which can be depicted graphically (Fig. 3). 5 4. Determining the inhibitory effect of a phosphatase inhibitor of PTP1 B. The test for determining the inhibitory effect of the active compound 2,2-dioxo-2,3 dihydro-2,6-benzo[1,2,3]oxathiazol-5-yl)-(9-ethyl-9H-carbazol-3-ylmethyl)amine using the DiFMUP test takes place in a black microtiter plate at a temperature of 0 370C. 120 p/1 volumes of reaction buffer are provided, with the buffer containing the following components: 100 ng of protein tyrosine phosphatase PTP1B/ml; 50 mM Hepes, pH 6.9; 150 mM NaCI; 1 mM EDTA; 2 mM DTT. To this are added 15 1l of the inhibitor solution to be tested, at a variety of concentrations. The phosphatase reaction is started by adding 15/pl of 1 mM DiFMUP solution and the fluorescence 5 (measured in RFU) is measured, at time intervals of 30 seconds and over a period of 15 minutes, in a fluorescence microtiter plate photometer at 358 / 455 nm. The measure of the enzyme activity is the increase in fluorescence, which can be depicted graphically (Fig. 1). The reduction in enzymic activity which is obtained depends on the concentration of inhibitor employed. The inhibitor concentration at .0 which the active compound 2,2-dioxo-2,3-dihydro-2,6-benzo[1,2,3]oxathiazol-5-yl) (9-ethyl-9H-carbazol-3-ylmethyl)amine reduces the activity of the PTPI1B by half (IC 50 ) can be determined to be 3.8 pM. The IC-50 values using the pNPP test method and the malachite green phosphopeptide test were determined for comparison. In this connection, the pNPP test method gives an IC50 value of 5.1 pM and the .5 malachite green phosphopeptide test method gives an IC50 value of 3.9 p/M. The corresponding inhibition curves are included in Fig. 4. 5. Characterizing the type of inhibition exerted by a phosphatase inhibitor on PTP1 b. 10 The reaction takes place in a black microtiter plate at a temperature of 37°C. 120 pl volumes of reaction buffer are provided, with the buffer containing the following components: 100 ng of protein tyrosine phosphatase PTP1b/ml; 50 mM Hepes, pH 6.9; 150 mM NaCI; 1 mM EDTA; 2 mM DTT and an inhibitor concentration which depends on the previously determined IC50. The phosphatase reaction is started by 14 adding 15 pl of DIFMUP solution, which contains the substrate at 10 times the desired final concentration in the final volume (Figure 2: 0 - 200 pm), and the fluorescence is measured, at time intervals of 30 seconds for a period of 15 minutes, in a fluorescence microtiter plate photometer at 358-455 nm until the reaction goes 5 into saturation. Subsequently, a 10-fold excess of the previously employed final concentration of substrate is added and the reaction continues to be monitored, at time intervals of 30 seconds for a period of 15 minutes, in a fluorescence microtiter plate photometer at 358-455 nm. The reaction cannot be restarted in the presence of irreversible inhibitors while it is possible to do this when the inhibition is of the 0 reversible type (Fig. 5). 6. Characterizing, by means of time-dependent incubation, the type of inhibition exerted by a phosphatase inhibitor on PTP1 b. 5 The reaction takes place in a black microtiter plate at a temperature of 37°C. 120 pl volumes of reaction buffer are provided, with the buffer containing the following components: 100 ng of protein tyrosine phosphatase PTP1b/ml; 50 mM Hepes, pH 6.9; 150 mM NaCI; 1 mM EDTA; 2 mM DTT and an inhibitor concentration which depends on the previously determined IC50. .0 The mixture is incubated and, at defined points in time, the phosphatase reaction is started by adding 15 pl of DIFMUP solution, which contains the substrate at 10 times the desired final concentration in the final volume (Figure 2: 0 - 200 pM), and the fluorescence is measured, at time intervals of 30 seconds for a period of 15 minutes, in a fluorescence microtiter plate photometer at 358-455 nm. .5 In the presence of irreversible inhibitors, the decrease in enzyme activity depends on the preincubation time, whereas this phenomenon cannot be observed in the case of inhibitors of the reversible inhibition type (Fig. 6). .0 List of the figures: Fig. 1: Cleavage of DiFMUP in dependence on the concentration of the PTP1B enzyme. Fig. 2: Concentration dependence of the cleavage of DiFMUP by PTPIB.

15 Fig. 3: Cleavage of DiFMUP in dependence on the concentration of the phosphotyrosine phosphatase enzymes PTPalpha, LAR, TCPTP, SHP 2, CD45 and YOP. Fig. 4: Determining the inhibitory effect exerted by a phosphatase inhibitor of PTP1B. 5 Fig. 5: Characterizing the inhibition type of a phosphatase inhibitor Fig.6: Characterizing, by time-dependent incubation, the inhibition type of a phosphatase inhibitor

Claims (17)

1. A method for detecting the enzymic activity of a protein tyrosine phosphatase in biological material, which comprises a] providing biological material or a preparation obtained from biological material, b] providing 6,8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), c] bringing the biological material or the preparation obtained from biological material from a] into contact with the DiFMUP from b] in an aqueous solution, d] fluorometrically detecting the 6,8-difluoro-4-methylumbelliferyl which is then formed.

2. The method as claimed in claim 1, wherein at least one protein tyrosine phosphatase from the group LAR, CD 45, YOP, PTP alpha, PTP 1B, TC-PTP, CDC 25, PTEN and SHP1,2 is provided as the preparation obtained from biological material.

3. The method as claimed in claim 1 or 2, wherein the concentration of the DiFMUP after the bringing-into-contact is 10- 250 pM.

4. The method as claimed in claim 3, wherein the concentration of the DiFMUP is from 50 to 100 pM.

5. The method as claimed in one or more of claims 1 to 4, wherein the pH of the aqueous solution in c] is between 5.0 and 8.0.

6. The method as claimed in claim 5, wherein the pH is between 6.0 and 7.5.

7. The method as claimed in claims 5 and 8, wherein the pH is 7.0. 17

8. A method for identifying a compound which modifies the activity of a protein tyrosine phosphatase, which comprises a] providing a chemical compound, b] providing biological material or a preparation obtained from biological material, c] providing 6,8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), d] bringing the chemical compound from a] and the biological material or the preparation obtained from biological material from b] and the DiFMUP from c] into contact with each other in an aqueous solution, e] fluorometrically determining the quantity of the 6,8-difluoro-4 methylumbelliferyl which is then formed, f] comparing the quantity, from e], of 6,8-difluoro-4-methylumbelliferyl which is formed with the quantity of 6,8-difluoro-4-methylumbelliferyl which is formed in a control assay.

9. The method as claimed in claim 8, wherein the activity of a protein tyrosine phosphatase is stimulated, inhibited or maintained.

10. The method as claimed in claim 8 or 9, wherein the protein tyrosine phosphatase is selected from the group LAR, CD 45, YOP, PTP alpha, PTP 1B, TC-PTP, CDC 25, PTEN and SHP1,2.

11. A compound which has been identified by a method as claimed in claims 8 to 10.

12. A compound as claimed in claim 11, wherein the mass of the compound is between 0.1 and 50 kDa.

13. A compound as claimed in claim 11 or 12, wherein the mass of the compound is between 0.1 and 5 kDa.

14. A compound as claimed in claims 11 to 13, wherein the mass of the compound is between 0.1 and 3 kDa. 18

15. A compound as claimed in one or more of claims 11 to 14, wherein the compound is a protein, an amino acid, a polysaccharide, a sugar, a polynucleotide, a nucleotide, a natural product or an aromatic hydrocarbon compound.

16. A pharmaceutical which comprises at least one compound as claimed in claims 11 to 15, auxiliary substances for formulating a pharmaceutical and/or polymeric additives.

17. The use of a compound as claimed in one or more of claims 11 to 14 for producing a pharmaceutical for treating diabetes.