WO2005070956A1

WO2005070956A1 - Analogues of antimicrobial peptide synthesized and produced from gaegurin 5

Info

Publication number: WO2005070956A1
Application number: PCT/KR2005/000028
Authority: WO
Inventors: Bong Jin Lee; Hyung Sik Won; Seo Jeong Jung; Hyung Eun Kim; Min Duk Seo
Original assignee: Seoul National University Industry Foundation
Priority date: 2004-01-06
Filing date: 2005-01-06
Publication date: 2005-08-04
Also published as: KR100547565B1; KR20050072337A

Abstract

The present invention is related to antibiotic peptides designed by systemic peptide engineering using Gaegurin 5 isolated from Korean frog (Rana rugosa), which have smaller structure compared with previously known Gaegurin peptides and shows potent antibiotic activity. Specifically, the antibiotic peptide of the present invention synthesized from the shortest length of Gaegurin named Gaegurin 5 among Gaegurins 1 to 6, show potent antibacterial activity against gram positive and negative strains, good safety with very low hemolytic activity and favorable advantages such as drug absorption and drug transport due to their advantageous structural property, which can be useful as a potent anti-bacterial or anti-fungal agent.

Description

ANALOGUES OF ANTIMICROBIAL PEPTIDE SYNTHESIZED

AND PRODUCED FROM GAEGURIN 5

Technical Field

[1] The present invention is related to analogues of antimicrobial peptide synthesized and produced from Gaegurin 5. Background Art

[2] The infection of bacterium is one of the common and fatal factors causing human disease. Unfortunately, the antibiotic abuse has given rise to antibiotic resistance till now. In fact, the expression of antibiotic resistance is faster than the development of the derivatives of new antibiotics. For example, the several bacteria such as En- terococcus faecalis, Mycobacterium tuberculosis or Pseudomonas aeruginosa, have shown resistance to the well known antibacterial agents till now (Stuart B. Levy., Scientific American, pp46-53, 1998).

[3] The antibiotic tolerance is distinguished from antibiotic resistance and has been discovered from Pneumococcus sp. for the first time in 1970's, which has provided with crucial clue to solve the mechanism of Penicillin.

[4] The growth of species showing tolerance to antibiotic was blocked in optimum concentration of antibiotic however, the antibiotics could not kill the bacteria eventually. The tolerance occurs in case antibiotics inhibit the cell wall synthetic enzyme and an autolytic enzyme of bacterium such as autolysin is not active. Accordingly, This fact manifests that penicillin kills bacterium by activating endogenous hydrolytic enzyme and the bacterium survives by inhibiting the activation of enzyme during antibiotic therapy.

[5] The bacterial tolerance is clinically very important since the efficacy of antibiotic therapy lowers in case that the eradication of the bacterium could not achieved thereby (Handwerger and Tomasz, Rev. Infec. Dis., 7, pp368-386, 1985). Furthermore, the tolerance occurrence is considered as an essential prerequisite to antibiotic tolerance since it enable the survival of several bacteria in spite of antibiotic therapy. Those bacteria can grow in spit of the presence of antibiotic due to the acquirement of new genetic elements having antibiotic resistance continuously. Actually, there have been reported that the bacteria having antibiotic resistance shows also antibiotic tolerance (Liu and Tomasz, J. Infet. Dis., 152. pp365-372, 1985). Accordingly, the development of new antibiotics which can kill the bacteria showing antibiotic resistance has been needed till now.

[6] Bacteria can kill neighboring bacteria by synthesizing peptides or small organic molecules, and those bacteriocin can be classified with three categories structurally: i.e., lantibiotics, non-lantibiotics and a bacteriocin secreted by signal peptides (Cintas et al., J. Bad., 180, ppl988-1994, 1998). The Animals including insects also can produce naturally forming peptide antibiotics, which can be classified into three groups structurally; i.e., cysteine-rich beta-sheet peptides, an amphipathic alpha helical molecules and proline-rich peptides (Mayasaki et al., Int. J. Antimicrob. Agents, 9, pp269-280, 1998). There have been reported that those anti-microbial peptides plays important roles in host defense and inherent immune system and the peptides have various structures according to their amino acid sequence, the structure of which abundant peptide has amphi-pathic alpha helical structure without cysteine residue such as cecropine, an anti-microbial peptide found in insects.

[7] Anti-biotic peptide acting on cellular membrane has been found in most of all the species in the world at now. Recently, the anti-biotic peptide has been paid attention to researchers to overcome above described problems, i.e., the increase of antibiotic resistant bacteria, Especially, after the first finding of bombinins from Bombina variegate in 1969, the skin of anurans (frogs and toads) has proven to be a rich source of antibiotic peptides with a broad-spectrum of antimicrobial activities. After the discovery of antibiotic peptide from African toenail frog, i.e., magainins in 1987, the frog skin antibiotic peptide has been increasingly focused as potential therapeutic agents.

[8] Since antibiotic peptides kill bacteria by acting on bacterial cell membrane and destroying the membrane selectively, the mechanism of antibiotic peptide is quietly different from that of the existing antibiotics and is valuable as alternative proposal for overcoming resistance problems. Furthermore, since the antibiotic peptides have broad spectrum of anti-microbial activities for gram-positive microbe, gram-negative microbe, fungus, virus and tumor cell and is natural substance isolated from natural resource, it is expected to be a good antibiotic showing no side effect. Additionally, since it shows amphipathic property i.e., soluble in both of water and lipid, it is expected to have great advantages in respect to drug absorption, drug transport etc. However, in spite of the above advantages of antibiotic peptides, there remain several problems, such as structural stability, bulky M. W. etc, in developing antibiotic peptide as a drug, the big problems of antimicrobial antibiotics are stability and molecular weight as follows: First, in aspect of stability, it is easily decomposed since the antibiotic peptides could not resist to lots of protein lyases existing in vivo. Those problems can be solved by introducing unnatural derived amino acid such as D- amino acid, beta- amino acid, modifying chemical structure and so on. However, another problem, i.e., the bulky size of antibiotic peptide having M. W. more than 3,000 still remains to solve in respect to the problems in drug absorption, drug transportation etc. [9] Accordingly, those problems can be solved by the discovery or design of smaller size of antibiotic peptide fundamentally.

[10] Therefore, the present inventors have endeavored to overcome the previously reported problems of antibiotic peptide and studied to find effective and novel peptide till now, finally, they have found the smallest length of Gaegurin 5 among six kinds of antibiotic peptides named as Gaegurin isolated from Korean frog, i.e., Gaegurin 1 to 6 and modified the structure of Gaegurin 5. The present invention was completed that present inventors confirmed the potent anti-microbial activity and hemolytic activity of the modified antibiotic peptide. Disclosure of Invention Technical Problem

[11] The present invention provides novel antibiotic peptide analogues synthesized and designed from Gaegurin 5 showing potent anti-microbial activity with broad spectrum and little hemolytic side effect, and the anti-bacterial and anti-fungal composition comprising the same.

Technical Solution

[12] Accordingly, it is an object of the present invention to provide novel antibiotic peptide analogue compound represented by F-L-G-W-L-F-K-N-A-S-K (A4W-GGΝ5Ν11) and F-L-G-A-L-F-K-W-A-S-K (V8W-GGN5N11).

[13] The above-described peptide is synthesized by the method characterized in substituting specific moiety of the peptide with tryptopan.

[14] It is an another object of the present invention to provide a pharmaceutical composition comprising above described antibiotic peptide designed and synthesized from Gaegurin 5 as an effective ingredient and pharmaceutically acceptable carrier or adjuvant as a anti-bacterial agent or anti-fungal agent.

[15] An inventive compound may be prepared in accordance with the following preferred embodiment.

[16] Hereinafter, the present invention is described in detail.

[17] An inventive compound designed and synthesized from Gaegurin 5 can be prepared in detail by following procedures;

[18] The inventive antibiotic peptide of the present invention can be synthesized and prepared through the peptide engineering modifying the structure of Gaegurin 5 having the shortest residue (24 residues) and Gaegurin 4 having the longest residue (37 residues) selected from the six kinds of antibiotic peptides isolated from Korean frog, i.e., Rana rugosa.

[19] Specifically, to synthesize optimized antibiotic peptide derivative, solid phase synthetic method using Fmoc amino group protecting vessel and Gaegurin 1 and 5 as parent structures.

[20] Preferably, the compounds of the present invention can be prepared by the steps consisting of: eliminating C-terminal residue of Gaegurin 4 side by side with identifying its antibiotic activity; removing C-terminal 14 residue to the extent that only 23 residue at N-terminal remains with checking their antibiotic activities to be disappeared; substituting the residue at positioned 16 in inactive Gaegurin 4 derivative with tryptophan residue to synthesize Gaegurin 4 derivative (D16W-GGN4N23) analogue showing antibiotic activity, which result confirms that the introduction of tryptophan thereto is a crucial requirement.

[21] With the identical method with above described method, the antibiotic activity is identified with eliminating C-terminal residue of Gaegurin 5 for Gaegurin 5 side by side, of which result confirmed that minimal requirement for the activity is the analogue having length of the residues is 13 and the introduction of tryptophan is crucial. As we mentioned above, since the introduction of tryptophan residue is crucial in peptide engineering development, the tryptophan residue in Gaegurin 5 may be substituted with inactive 11 -residue fragment instead of active 13-residue fragment to afford 11 kinds of tryptophan substituted Gaegurin 5 analogues. At the result of identifying the bioactive activity of the analogues, tryptophan introduced A4W-GGN511 and N8W-GGN5N11 analogues into respective position 4 and 8 showed similar activity to parent molecules, i.e., Gaegurin 5. Furthermore, whether the introduction of only tryptophan into position 4 and 8 is specific or not, the introduction of other amino acids, preferably, Leucine having hydrophobic residue, Lysine having hydrophilic and cationic ions, and Phenylalanine having aromatic ring similar to tryptophan could be performed to synthesize seven kinds of amino acid substituted Gaegurin 5 analogues.

[22] Additionally, the antibiotic peptide of the present invention could be prepared by various methods including above described synthetic method as well as genetic re- combinant technique method, for example, gene clone including DNA or RNA sequence coding antibiotic peptide is prepared to be suitable to express above described antibiotic peptide and the gene clone is transformed into appropriate cells to express and obtain purpose above described anti-biotic peptide.

[23] The present invention also provides antibiotic peptide prepared by above described method.

[24] The present invention provides a pharmaceutical composition comprising above described antibiotic peptide as an effective ingredient and pharmaceutically acceptable carrier or adjuvant as an anti-bacterial agent or anti-fungal agent.

[25] To investigate the most property-optimized antibiotic peptide analogues in respect to molecular weight and stability among antibiotic peptides prepared by above described preparing method, the antibiotic activity and hemolytic activity of those analogues were examined and the results indicated that following antibiotic peptide analogues showed similar anti-bacterial activity and hemolytic activity to Gaegurin 5:

[26] GGN5N13: F-L-G-A-L-F-K-V-A-S-K-V-L

[27] A4W-GGN5N11: F-L-G-W-L-F-K-V-A-S-K

[28] V8W-GGN5N11: F-L-G-A-L-F-K-W-A-S-K

[29] In the contrary, that following antibiotic peptide analogues showed similar antibacterial activity to Gaegurin 5, however, they showed potent hemolytic activity:

[30] A4L-GGN5N11 : F-L-G-L-L-F-K-V-A-S-K

[31] V8L-GGN5N11 : F-L-G-A-L-F-K-V-A-S-K

[32] W4, 8-GGN5N11 : F-L-G-W-L-F-K-W-A-S-K

[33] It is confirmed that the other antibiotic peptide analogues showed rarely antibacterial activity. After the monitoring whether the antibiotic peptide analogues have structurally similarity to Gaegurin 5, favorable advantage in respect to anti-bacterial activity and hemolytic activity, it is confirmed that minimal number of residue among 23 residues in amino acid to obtain above advantages is 11 and the analogues have amphipathic property by prepared through the tryptophanyl substitution at the positions between hydrophilic end side and hydrophobic starting side. Through above described results, it is conformed that the most property-optimized antibiotic peptide analogues are A4W-GGN5N11 and V8W-GGN5N1 las described above.

[34] The antibiotic peptide analoguesaccording to the present invention can be provided as a pharmaceutical composition containing pharmaceutically acceptable carriers, adjuvants or diluents. For example, the compound of the present invention can be dissolved in oils, propylene glycol or other solvents which are commonly used to produce an injection. Suitable examples of the carriers include physiological saline, polyethylene glycol, ethanol, vegetable oils, isopropyl myristate, etc., but are not limited to them. For topical administration, the compounds of the present invention can be formulated in the form of ointments and creams.

[35] Hereinafter, the following formulation methods and excipients are merely exemplary and in no way limit the invention.

[36] The compound of the present invention may be formulated into preparations for injections by dissolving, suspending, or emulsifying them in aqueous solvents such as normal saline, 5% Dextrose, or non-aqueous solvent such as vegetable oil, synthetic aliphatic acid glycerides, esters of higher aliphatic acids or propylene glycol. The formulation may include conventional additives such as solubilizers, isotonic agents, suspending agents, emulsifying agents, stabilizers and preservatives.

[37] The compound of the present invention mixed with pharmaceutically acceptable carrier together with physiological saline or organic solvent and other components, for examples, carbohydrates such as glucosem sucrose or dextrin, antioxidants such as ascorbic acid or glutathion, chelating agents, low molecular protein or other stabilizer may be mixed thereto for improving their stability or absorption.

[38] The desirable dose of the inventive compound varies depending on the condition and the weight of the subject, severity, drug form, route and period of administration, and may be chosen by those skilled in the art. However, in order to obtain desirable effects, it is generally recommended to administer at the amount ranging 0.0001-100 mg/kg, preferably 0.001-100 mg/kg, more preferably 0.1 to 2 mg/kg by weight/day of the inventive compound of the present invention. The dose may be administered in single or divided into several times comprising twice or three times a day. In terms of composition, the compounds should be present between 0.0001 to 10% by weight, preferably 0.0001 to 1% by weight based on the total weight of the composition.

[39] The pharmaceutical composition of present invention can be administered to a subject animal such as mammals (rat, mouse, domestic animals or human) via various routes. All modes of administration are contemplated, for example, administration can be made orally, rectally or by intravenous, intramuscular, subcutaneous, intrathecal, epidural or intraperitoneal injection, For example, the compound of the present invention can be administrated at single dose through short-term infusion or bolus formulation or fractionated treatment protocol administrated for a long period with multiple dosages. The drug concentration of the present invention can be determined appropriately in consideration with various factors such as administration routes, patient'age or health condition etc.

[40] The present invention is more specifically explained by the following examples.

However, it should be understood that the present invention is not limited to these examples in any manner.

Advantageous Effects

[41] The antibiotic peptides designed and synthesized from Gaegurin 5 of the present invention show potent antibacterial activity against gram positive and negative strains, good safety with very low hemolytic activity and favorable advantages such as drug absorption and drug transport due to their advantageous structural property i.e., the shortest structure among previously known antibiotic peptides. Brief Description of the Drawings

[42] Fig. 1 shows side view of the whole GGN5 structure in SDS micelles;

[43] Fig. 2 shows top view of the N-terminal part (G3-V13) in the amphipathic a-helix regionin SDS micelles;

[44] Fig. 3 representsSequence alignment of GGN5 and its analogue peptides;

[45] Fig. 4 representsHelical wheel diagrams of A4W(or V8W)-GGN5^Nπ (left); [46] Fig. 5 represents Helical wheel diagrams of D16W-GGN4 (right);

[47] Fig. 6 depictsTime-kill curves of GGN5, A4W-GGN5^N11, and V8W-GGN5^N11 against E. coli and S. aureus;

[48] Fig. 7 depictsCD results of A4W-GGN5^N1 and V8W-GGN5^{N1 λ} ;

[49] Fig. 8 depictsNMR results of A4W-GGN5^N11 and V8W-GGN5^N11 .

Best Mode for Carrying Out the Invention

[50] It will be apparent to those skilled in the art that various modifications and variations can be made in the compositions, use and preparations of the present invention without departing from the spirit or scope of the invention.The present invention is more specifically explained by the following examples. However, it should be understood that the present invention is not limited to these examples in any manner. Mode for the Invention

[51] The following Reference Example, Examples and Experimental Examples are intended to further illustrate the present invention without limiting its scope.

[52] Example 1. Peptide Synthesis and Purification

[53] To prepare the most property-optimized antibiotic peptide analogues having amphipathic property, novel smaller sized antibiotic peptides were investigated using parent molecule, i.e., Gaegurin 5 peptide isolated from the skin of Korean frog (Rana rugosa) according to solid-phase methods using standard Fmoc chemistry disclosed in literature (Wellings D. A. and Atherton, E., Methods Enzymol., 289, pp44-67, 1997).

[54] Peptides were synthesized automatically on a peptide synthesizer (Model 90,

Advanced Chemtech, Inc.). 70mM Rink Resins obtained from Advanced Chemtech, Inc. was added to reaction vessel. The mixture of 2 equivalent amount of amino acid, 3 amount of HOB T (1-Hydroxybenzotriazole) and 2 equivalent amount of DIC (1,3-Diisopropylcarbodiimde) to amino acid was added to amino acid vessel and dissolved in 10 ml of DMF (Dimethylformamide). The resin in reaction vessel was subjected to swelling procedure using by DMF solvent. The Fmoc (9-fluorenylmethoxycarbonyl) residue in the resin was eliminated using by 25% piperidine/DMF mixture solvent. The dissolved amino acid in amino acid vessel was transferred to reaction vessel and reacted with resin fir 2 or 3 hrs. Above step was performed repeatedly to linking with amino acid and the Fmoc residue at N-terminal moiety in last amino acid was removed using by 25% piperidine/DMF mixture solvent. The protecting groups attached to lysine or serine residue was eliminated and reacted with 20 ml of 10% TFA (Trifluoro acetic acid)/DCM for 4 hrs to isolate the synthesized peptides from resin. The solid resin was filtered from the solution and the filtered solution was added to round flask to distillate. After the distillation of the solvent, 10 ml of 20% acetonitrile containing 0.1% TFA was added thereto to re- dissolve and remaining solution was filtrated using centrifuger or filter. The supernatant was lyophilized and subjected to purification using by analytical reverse phase HPLC on C-18 column (eluting solution: mixture solution of acetonitrile and water containing 0.1% trifluoroacetic acid, fluid velocity: lml/min) for 45 mins to collect detected fractions comprising only purposed peptides. The peptides were subjected to lyophilization and their M. W, were determined. The sequence lists of the synthesized Gaegurin antibiotic peptides were shown in Fig.3.

[55] Experimental Example 1. Determination of Antibiotic activity

[56] To determine the regulating activity of the compound prepared by Example 1 on the antibiotic activity, following experiments were performed.

[57] 1-1. Determination of MIC

[58] Antimicrobial activity was determined by the standard broth microdilution method by measuring the MIC values against diverse microorganisms. In brief, Luria-Bertani medium was used as a Broth medium. 30 micro-liter of sample (2mg/ml) prepared from Example 1 and 270 micro-liter of fluid medium were added to lane 1 well of 96- well microtiter plates and to remaining lanes of the wells, 150 micro-liter of medium was only added. 150 micro-liter of sample solution in lane 1 was mixed with lane 2 to prepare diluted solution (x 2). With similar diluting method to above described method, serial dilution was performed to prepare 150 microliter of diluted drug solution (x2) having final drug concentration in the range from 1.6 to 200 microgram/ml in respective well. 25 microliter of the cell culture being grown to 10 - 10 colony forming unit/ml in 3ml of broth was added to each well and the microtiter plate was incubated for overnight at 37°C. The growth of the bacteria was determined by evaluating the UN absorbance of each sample solution at 630nm and the MIC was defined as the lowest peptide concentration that completely inhibits the cell growth.

[59] At the result, A4W-GGΝ5Ν11 and V8W-GGN5N11 showed potent antibiotic activity for various strains compared to that of Gaegurin 5 as can be shown in Table 1 to 3.

[60] 1-2. Determination of Hemolysis

[61] Hemolytic activities were measured as follows:

[62] 3ml of blood sample collected from healthy male was mixed with PBS (phosphate buffered saline, isotonic solution) with a ratio 1 : 1 (v/v), centrifuged to remove buffy coat and blood plasma and washed with physiological saline solution at three times to isolate pure erythrocyte. The erythrocyte was suspended with 20ml of PBS and pre- incubated in water bath at 37°C for 15 mins. 10ml of peptide solution was mixed with 190ml of erythrocyte solution in order to prepare various mixed solution containing various final concentrations of the peptides, i.e., 100, 50, 25 mg/ml and the solution was incubated in water bath at 37°C for 15 mins, centrifuged. 100ml of the supernatant was diluted with 1ml of PBS and the absorbance at 550nm was determined. The relative attenuation, as compared with that of the suspension treated with 0.2% Triton X-100, was defined as the percentage of hemolysis.

[63] At the result, A4W-GGN5N11 and V8W-GGN5N11 showed mere hemolytic activity similar to their parent molecule, i.e., Gaegurin 5 as can be shown in Table 1 to 3. Accordingly, it is confirmed that the compounds are safe and suitable to drug development, particularly, N8W-GGN5N 11 showed much less hemolysis than A4W-GGN5N11.

[64]

[65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] Table 1

[82] Table 2

[83] Table 3

[84] 1-3. Time-Kill Curve Analysis

[85] To identify whether the antibiotic activity confirmed by MIC test denotes bacterial activity killing bacterial cell or bacteriostatic activity inhibiting the growth or differentiation of bacterial cell, the killing curve assay in a standard protocol was performed against two different strains: Staphylococcus aureus, a Gram-positive bacterium, and Escherichia coli, a Gram-negative bacterium as follows:

[86] Briefly, testing strain was incubated in 2ml of LB agar plate for overnight and

2mg/ml of individual antibiotic peptide prepared in Example 1 was diluted to prepare 2ml of cell cultures containing various concentrations (at Ox, 0.25x, 0.5x, lx, 2x, and 4xMIC) of the peptides. 20 microliter of culture strain (about 10 CFU/ml) was added to 2ml of new LB agar medium. 20 microliter of the solution was added to each 5 dilution solution in order to prepare bacterial concentration be about 10 CFU/ml (diluting to xlO to 10 ). The solution was further incubated at 37°C and respective sample collected at 0, 2, 4, 6, and 24h of incubation, was subjected to sub-culture. The subculture was performed by follows: each 270 microliter of 0.9% NaCl was added to each well of 96-well microtiter plate and 30 microliter of six samples were added to each first lane well to prepare 10 folds diluted solutions. With similar diluting method to above described method, serial dilution was performed to prepare various concentrations of diluted drug solution (10¹, 10^"2, 10^"3, 10^"4, 10^"5, 10^"6, 10^"7, and 10^"8-fold dilutions). 100 microliter of each dilution was spread onto LB-agar plate and incubated at 37°C for overnight. After the incubation, CFU/ml was calculated by multiplying the dilution folds forming appropriate number of colony countable by naked observation by formed colony number and log 10 (CFU/ml) according to the time for each drug concentration was plotted.

[87] At the result, A4W-GGN5N11 and V8W-GGN5N11 showed bacteriocidal activity killing survived bacteria similar to their parent molecule, i.e., Gaegurin 5. Accordingly, it is confirmed that the compounds can selectively kill bacterial cells without any side effect on human cell in although they have smaller sized structure than parent molecule, i.e., Gaegurin 5.

[88] Experimental Example 2. The structure-function correlation analysis

[89] 2-1. Circular Dichroism (CD)

[90] For CD spectroscopy, a precise amount of the peptide powder was dissolved to a final concentration of 50 mM, in various solvents: 20 mM sodium acetate buffer (pH 4.0), TFE/water mixtures, 5 mM DPC micelles, and 10 mM SDS micelles. Before the CD measurement, the pH was adjusted to 4.0 by the addition of 0.1 N HC1 or NaOH. CD spectra were obtained at 20°C on a JASCO J-720 spectropolarimeter, using a 0.2 cm path-length cell. CD scans were taken at 293 K from 250 nm to 190 nm, with a 1 nm bandwidth, a 4 sec response time, a scan speed of 50 nm/min, and a 0.5 nm step resolution. Three scans were added and averaged, followed by subtraction of the CD signal of the solvent. Finally, the CD intensity was normalized as the mean residue molar ellipticity calculated by following empirical formulae 1 :

[91] [Empirical Formulae 1]

[92]

[93] wherein i^ mr.w.

2- 1

(deg-cm dmol^" ) and mdeg) denotes mean molar ellipticity and CD intensity determined at specific wavelength lambda respectively; 1, c and n denotes diameter of determined cells (cm), sample concentration (mM) and the number of residue respectively.

[94] At the result, A4W-GGN5N11 and V8W-GGN5N11 showed similar CD spectral change in various kinds of solvents to its parent molecule, i.e., Gaegurin 5 as can be shown in Fig. 7.

[95] 2-2. NMR analysis [96] Samples for NMR measurements contained 3 mM peptide in a 300 mM SDS-_i solution containing 7% D O at pH 4.0. Two-dimensional DQF-COSY, TOCSY (60 ms mixing time), and NOESY (200 ms mixing time) spectra were recorded on a Bruker DRX-500 spectrometer at 313 K. Solvent suppression was achieved using selective pre-saturation method. Determined NMR data was analyzed by using NMR Pipe/NMR Draw and NMR View program and DDS (sodium

4,4-dimethyl-4-silapentane-l-sulphonate) used as a standard material for H chemical shift. NMR analysis was performed by using standard method cited in the literature (Wuthrich, K., NMR of proteins and Nucleic Acids, John Wiley and Sons, New York, 1986).

[97] Sequence-specific assignments of the proton resonances were achieved by spin system identification from the TOCSY and DQF-COSY spectra, followed by sequential assignments through the NOE connectivities.

[98] At the result, more detailed structure information can be obtained through NMR analysis and it is confirmed that both of A4W-GGN5N11 and V8W-GGN5N11 showed stable helix structure ranging from Gly 3 or Leu 2 residue to Ser 10 or Lys 11 residue as can be shown in Fig. 8.

[99] 2-3. Fluorescence analysis

[100] Fluorescence emissions of 5 mM peptide and NATA dissolved in various solvents

(water, 10 mM SDS micelles, and 5 mM DPC micelles, respectively, at pH 4.0) were monitored on a JASCO FP-6500 spectrofluorometer at 20 °C, using a 10 mm quartz cell. An excitation wavelength of 295 nm was used, to ensure that the light was absorbed almost entirely by tryptophanyl groups. Emission scans were taken from 300 nm to 450 nm, with a 5 nm excitation and emission bandwidth, a 0.5 sec response time, and a scan speed of 1000 nm/min. The fluorescence quenching experiment was performed by the standard method suggested by Eftink and Ghiron (Eftink, M. R. Ghiron, C. A., Biochemistry, 15, pp672-680, 1976; Eftink, M. R. Ghiron, C. A., J. Phys. Chem., 80, pp486-493, 1976; Eftink, M. R. Ghiron, C. A., Biochemistry, 16, pp5546-5551, 1977). The fluorescence emission was quenched by the progressive addition (4 ml at each time) of an 8 M acrylamide solution into the 2 ml sample solution. K (collisional or Stern-Nolmer quenching constant) was determined together with V (static quenching constant), by plotting F /(F-e ) versus the molar concentration of the quencher ([Q]; [Ac] in this work using acrylamide) for various V until a linear plot was obtained, according to the modified Stern-Nolmer equation expressed by following empirical formula 2:

[101] [Empirical Formulae 2]

[102]

= K„ > \ Q \)+1

F / c p [103] wherein F and F mean the fluorescence intensity at 1 (the wavelength where the

0 max maximum intensity F is observed) in the presence and absence of quencher, re- max spectively.

[104] At the result, it is confirmed that both of peptides showed a large blue shift of 1 max by more than 10 nm, when the solvent was changed from water to detergent micelles. The values of collisional quenching constant (K ) obtained from above quenching experiment and normal quenching parameters (V ) in H 0 were remarkably more reduced than in detergent micelles such as DPC and SDS as can be seen in following Table 4.

[105] Table 4

[106] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. Industrial Applicability

[107] As described in the present invention, above described antibiotic peptides designed and synthesized from Gaegurin 5 of the present invention show potent antibacterial activity against gram positive and negative strains, good safety with very low hemolytic activity and favorable advantages such as drug absorption and drug transport due to their advantageous structural property i.e., the shortest structure among previously known antibiotic peptides, the compounds can be useful as a potent antibacterial or anti-fungal agent.

[108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126]

Claims

[1] Novel antibiotic peptide analogue compound represented by F-

L-G-W-L-F-K-V-A-S-K (A4W-GGN5N11) synthesized and designed from

Gaegurin 5 . [2] Novel antibiotic peptide analogue compound represented by F-

L-G-A-L-F-K-W-A-S-K (V8W-GGN5N11) synthesized and designed from

Gaegurin . [3] The compound according to claim 1, wherein said peptide is synthesized by the method characterized in substituting specific moiety of the peptide with

Tryptopan. [4] A pharmaceutical composition comprising said antibiotic peptide compounds as set forth in claim 1 or 2 as an effective ingredient and pharmaceutically acceptable carrier or adjuvant as an anti-bacterial agent. [5] A pharmaceutical composition comprising said antibiotic peptide compounds as set forth in claim 1 or 2 as an effective ingredient and pharmaceutically acceptable carrier or adjuvant as an anti-fungal agent.