CN111018965B - Purification method of recombinant parathyroid hormone PTH (1-34) - Google Patents

Abstract

The application discloses a method for separating and purifying recombinant parathyroid hormone PTH, which comprises the following steps: 1) Bacteria are crushed and inclusion bodies are treated, bacteria are crushed through high-pressure homogenization, high-speed centrifugation is carried out after bacteria are crushed, sediment is collected, and the sediment is mixed with a compound solution for re-dissolution after re-suspension washing; 2) Affinity chromatography; the filler is selected from one of Ni-NTA, GST Sepharose and MBP Sepharose; 3) Enzyme cutting and renaturation on the column; 4) Cation exchange chromatography and/or hydrophobic chromatography; 5) Desalting. The invention can efficiently extract the PTH (1-34) polypeptide with biological activity from the inclusion body, thereby enabling the large-scale industrial production of the PTH (1-34) to be possible.

Description

Purification method of recombinant parathyroid hormone PTH (1-34)

Technical Field

The invention belongs to the technical field of protein separation and purification, and particularly relates to a method for separating and purifying recombinant parathyroid hormone PTH (1-34).

Background

Parathyroid hormone (Parathyroid hormone, PTH) is a polypeptide hormone consisting of 84 amino acids, synthesized, stored and secreted by parathyroid epithelial cells. PTH entering blood circulation can be rapidly converted into two peptide fragments of an amino terminal and a carboxyl terminal, wherein the peptide fragment of amino terminal 1-34 amino acid residues has complete PTH biological activity, blood calcium concentration and bone metabolism are regulated, the immune activity is small, and the peptide fragment of the carboxyl terminal is PTH immune activity polypeptide, and the biological effect is not quite clear.

PTH mainly exerts its biological function against osteoporosis, and its effect on bone formation is mainly produced by acting on bone tissue cells and tubular epithelial cells. For tubular epithelial cells, PTH mainly increases the reabsorption of calcium from the distal tubular and indirectly promotes the absorption of calcium from the intestinal tract by increasing the production of active vitamin D by the kidneys, and together increases the blood calcium concentration, which is beneficial to bone formation. It has effects of promoting bone resorption and bone formation for bone tissue.

Recombinant human PTH (1-34) was developed by Eli Lilly, inc. in the United states as early as nineties in the last century and was designated as Teripaolide for use in the treatment of osteoporosis. Some research and development units and enterprises in China are developing recombinant human parathyroid hormone, at present, the product of Shanghai combined Sier, xinlitai, has obtained production lot parts, some parts are in preclinical research or clinical research, and some parts enter a clinical test stage.

For the purification method of the product, patent technology is disclosed, such as CN102993293A, CN102731643A, CN1212336C and the like. However, these methods generally have the problems of influence on polypeptide activity, easy degradation of polypeptide, low yield, complex process flow and the like, which require the use of organic solvents. To solve the above problems, further studies on purification methods are still necessary.

Disclosure of Invention

Aiming at the technical problems, the invention discloses a simple purification method which can efficiently extract the PTH (1-34) polypeptide with biological activity from inclusion bodies, thereby enabling large-scale industrial production of the PTH (1-34) to be possible.

The invention discloses a method for separating and purifying recombinant parathyroid hormone PTH, which comprises the following steps:

1) Bacterial disruption and inclusion body treatment

High-pressure homogenizing to break bacteria, high-speed centrifuging to collect precipitate, re-suspending and washing the precipitate, and re-dissolving the precipitate in re-dissolving solution

2) Selecting proper affinity chromatography filler according to the tag peptide fragment of the fusion protein to carry out affinity chromatography; the filler is selected from one of Ni-NTA, GST Sepharose and MBP Sepharose;

3) Enzyme digestion and renaturation on column

Wherein the enzyme is selected from one of TEV enzyme, EK enzyme and Xa factor protease;

4) Cation exchange chromatography and/or hydrophobic chromatography

The stuffing of the cation exchange chromatographic column is selected from one of SP Sepharose HP, SP Sepharose FF, capto SP and Capto MMC;

the filler of the hydrophobic chromatographic column is selected from one of HP or FF fillers of Phynel, octyl or Butyl;

5) Desalting.

In one embodiment according to the invention, in step 1), step 1) comprises:

the weight of the thallus and the solution A is as follows: volume ratio 1: mixing at a ratio of 5-10, and pre-cooling to 1-4deg.C.

In one embodiment according to the invention, step 1) comprises:

homogenizing at 1-4deg.C under 60-80Mpa for 3-5 times; centrifuging the liquid after bacteria breaking at 4 deg.C and 10,000-15,000g for 15-30min, and collecting precipitate for use.

In one embodiment according to the invention, step 1) comprises:

re-suspending inclusion bodies in a re-suspension, the inclusion bodies and the weight of the re-suspension: the volume ratio is 1:5-10, stirring for 15-30min by a magnetic stirrer, centrifuging for 15-30min by 10,000-15,000g, and collecting precipitate for later use; the heavy suspension is solution A containing Triton X1000, tween20, tween80 or sacosyl with a final concentration of 0.5% -1.5%.

In one embodiment according to the invention, step 1) comprises:

the weight is as follows: the volume ratio is 1:5-10, adding a complex solution to resuspend inclusion bodies, uniformly mixing, centrifuging and collecting supernatant for later use; the compound solution takes solution A as a solvent and contains 8M urea, 6M guanidine hydrochloride or mixed solution of 2mol/L urea and sacosyl with the final concentration (volume percent concentration) of 0.3 percent.

In one embodiment according to the invention, step 2) comprises:

the ratio of the wet weight of the bacterial cells to the filler is 10:1-2, uniformly mixing the re-dissolved inclusion body with the filler, and further removing the impurity protein on the filler by using a solution A containing 20-25mM imidazole and 8M urea;

preferably, the column packing is washed with a few volumes of water before mixing with the reconstituted inclusion bodies, and then equilibrated with solution A containing 8M urea.

In one embodiment according to the invention, step 3) comprises:

adding a proper amount of protease with His tag into the affinity, and performing enzyme digestion on a column, wherein the enzyme digestion liquid is A liquid containing 2-4M urea or guanidine hydrochloride, the dosage of the enzyme digestion liquid is 1-2 times of that of the filler, and the enzyme digestion condition is 4-25 ℃ for enzyme digestion for 2-5 hours; wherein, the weight-volume ratio of the inclusion body to the enzyme is 10 in terms of g: ml: 1.

in one embodiment according to the invention, said step 4) comprises:

collecting the sample after affinity chromatography or hydrophobic chromatography, diluting 3-6 times with solution B and adjusting pH to 6.5; then the C liquid is used for linear gradient elution, the elution flow rate is set to be 5ml/min, the elution gradient is from 0 to 50% of the B liquid, and the elution volume is 10 column volumes; wherein the solution B is 20mM Phosphate Buffer (PB) with pH of 6.5; the solution C was 20mM Phosphate Buffer (PB) at pH6.5 containing 1M NaCl.

In one embodiment according to the invention, said step 4) comprises:

mixing a sample obtained by affinity chromatography or cation exchange chromatography with 3M ammonium sulfate solution to a final concentration of ammonium sulfate of 1-1.5M;

loading the sample by using a D liquid equilibrium chromatography system and a chromatography column, eluting by using a B liquid linear gradient after loading, wherein the elution flow rate is 5ml/min, the elution gradient is from 0 to 100% of the B liquid, the elution volume is 10 column volumes, and collecting protein and storing at 4 ℃; the solution D is 20mM phosphate buffer solution containing 1-1.5M ammonium sulfate with pH of 6.5.

In one embodiment according to the invention, said step 5) comprises:

the desalting is achieved by one selected from ultrafiltration, diafiltration, molecular sieves or desalting columns.

The invention is characterized and innovated in that:

by adopting the purification method, the target protein with the purity of more than 98 percent and the recovery rate of more than 40 percent can be obtained from the engineering bacteria of the escherichia coli for expressing PTH (1-34). The N, C end sequence was found to be consistent with theory by amino acid sequence determination. The mass spectrum detection molecular weight is about 4117 daltons, which accords with the theoretical value. Cell experiments prove that the compound has good cAMP secretion stimulating capability, and is not lower than a standard product purchased by Sigma company, so that the compound has good biological activity.

In addition, the method is a non-HPLC purification method, and the damage of organic solvents and the like to the activity of the protein is avoided. The method successfully realizes on-column enzyme digestion, enzyme digestion and renaturation are synchronously carried out, and the purification process is greatly shortened. The method is simple to operate, does not need special instruments, equipment, reagents and the like, and is beneficial to industrial expansion production.

Drawings

FIG. 1 is a flow chart of a purification process for PA5055

FIG. 2 is a cationic analysis; wherein small amounts of the hetero-protein are present in the flow-through sample, and the peak at the time of elution is collected for subsequent purification.

FIG. 3 is a hydrophobic chromatography; the front peak is hetero protein and the back peak is PTH (1-34) when eluting;

FIG. 4 shows the result of SDS-PAGE electrophoresis of the protein stock solution;

FIG. 5 shows the HPLC detection result of protein PTH (1-34) protein stock solution.

Detailed Description

The following examples are illustrative of the present application, but are not intended to limit the scope of the present application.

Specific embodiments of the present application will be described in more detail below. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

As used throughout the specification and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description hereinafter sets forth the preferred embodiment for carrying out the present application, but is not intended to limit the scope of the present application in general, as the description proceeds. The scope of the present application is defined by the appended claims.

Experimental reagent and material

1. Strains, plasmids

Strain BL21 (DE 3), DH5alpha E.coli was purchased from Novagen; the strain XL-1blue escherichia coli is a product of Agilent company in the United states; plasmid pGEX-6p-2 is a product of GE Healthcare, USA; plasmid pET32a, pET39b (+) is a product of the company Merck, USA; pMal-c4X is a NEB company product; pCOLD-SUMO was purchased from Soxhaust corporation.

2. Reagent(s)

TEV enzyme and EK enzyme are purchased from Biyun biotechnology Co., ltd.

PrimeSTAR HS DNA polymerase, DNA molecular weight standard, restriction endonuclease, protein molecular weight standard, DNA ligase, point mutation kit (mutanBest) and the like are products of Dalianbao organisms (TakaRa); plasmid extraction kits and gel recovery kits are products of Omega company, usa; peptone and yeast extract were purchased from Oxfoid corporation and medium was purchased from Beijing Obock Biotechnology Co.

PBS (Potassium dihydrogen phosphate (KH) ₂ PO ₄ ) 0.2g (homemade analytical grade), disodium hydrogen phosphate (Na ₂ HPO ₄ ·12H ₂ O) 2.9g (analytical grade at home), sodium chloride (NaCl) 8.0g (analytical grade at home), potassium chloride (KCl) 0.2g, water to 1000mL, pH 7.4); 20mol/L PB buffer: monopotassium phosphate (KH) ₂ PO ₄ ) 0.2g of phosphoric acidDisodium hydrogen (Na) ₂ HPO ₄ ·12H ₂ O) 2.9g, potassium chloride (KCl) 0.2g, water to 1000mL, pH6.0; ampicillin, kanamycin (north China pharmaceutical); 5 x protein loading buffer: 250mmol/L Tris-HCl (pH 6.8), 10% (W/V) SDS, 0.5% (W/V) bromophenol blue, 50% (V/V) glycerol, 5% (W/V) beta-mercaptoethanol; glutathione sepharose 4B (GE Healthcare company, usa); ni-NTA was purchased from Novagen. The rest reagents such as agar powder, tween-20 and the like are purchased in domestic markets.

In order to make the purposes, technical schemes and advantages of the invention more clear, the recombinant engineering bacterium pET28a-PTH (1-34)/BL 21 constructed in the room below (the engineering strain sequentially introduces His tag, SUMO tag and enzyme cleavage site of TEV at the N end of PTH (1-34), the His tag is favorable for subsequent purification, the SUMO tag is favorable for protein folding and renaturation, and the N end of PTH (1-34) can be ensured to have no residual amino acid after TEV enzyme cleavage) is taken as an example, and the invention is further described in detail with reference to the accompanying drawings and examples. The purification process flow of the present invention is shown in FIG. 1.

EXAMPLE 1 construction and expression of recombinant PTH (1-34) engineering bacteria

PTH (1-34) is the amino acid sequence of SEQ ID NO. 1, and the coding DNA code is optimized to be SEQ ID NO. 2.

Three genes of TEV enzyme cutting site (ENLYFQ), enterokinase enzyme site (DDDDK) and Xa factor enzyme cutting site (IEGR) are respectively added at N end of PTH (1-34), 3 (GGGGS), his6 and SSGSSG are sequentially added from right to left, bamHI site GGATCC is added at 5 'end of each gene, termination code TGATAA, hindIII site AAGCTT and NotI site GCGGCCGC are added at 3' end, and the sequence is synthesized by Shanghai bioengineering limited company.

The three genes synthesized by double cleavage with BamHI+HindIII and BamHI+NotI and the vectors shown in Table I were collected to obtain the desired fragment and the vector, respectively. Construction of recombinant expression vectors was performed in the manner of Table 1.

TABLE 1 construction of recombinant PTH (1-34) expression vectors

The complete synthesis FH8 gene (SEQ ID NO: 3) is synthesized by the Shanghai biological engineering Co., ltd, and is filled into pET22b and pET28a, the DNA sequence encoding- (GGGGS) n-TEVs-PTH is designed and amplified by primer pair, pET22b and pET28a are respectively amplified, and recombinant vectors pET22b-FH8- (GGGGS) n-TEVs-PTH and pET28a-FH8- (GGGGS) n-TEVs-PTH are constructed by homologous recombination kit Mut Express MultiS Fast Mutagenesis Kit V2 according to the manufacturer's specification. The recombinant plasmid was transformed into E.coli DH5alpha.

The positive clones obtained in the two steps were cultured and plasmid-extracted, and E.coli XL1-Blue (pGEX-6P-2) and BL21 (DE 3) (other plasmids) were transformed after the plasmids were identified correctly.

Example 2: optimized construction of recombinant PTH (1-34) engineering bacteria

Preliminary results are summarized in Table 2 by summarizing the fusion proteins expressed by the recombinant vectors constructed in example 1,

TABLE 2 expression of recombinant engineering bacteria

If the fusion protein is a fusion protein which can be expressed in a soluble way, the obtained target protein PTH (1-34) is in an oxidized form; if the expression is inclusion body expression, the protease enzyme digestion can be carried out only by completely renaturating the fusion protein, the old way of preparing the target protein is also obtained, the reverse phase purification step is added in the purification process, and a large amount of organic solvents are used in the preparation process.

In order to overcome the defects of the prior art, the optimal construction strategy of the recombinant PTH (1-34) engineering bacteria is as follows: recombinant fusion proteins are expressed in the form of a more open inclusion body, whereas fusion proteins can renature in the presence of higher concentrations of urea and are more easily cleaved by TEV enzymes that are more economical to produce.

The PCR method is used for optimizing each element in front of the guide peptide, and the combination of various forms and repeated screening are carried out. The feature of helping the fusion protein fold and increasing the solubility is utilized; and the characteristics of high expression quantity of the pET28a vector and further improvement of the expression quantity of the expression enhancement peptide are utilized. Non-compact inclusion bodies are formed by counteracting solubility by SUMO through rapid expression. Finally, the recombinant PTH (1-34) engineering strain, namely pET28 a-expression enhancement peptide-connecting peptide 1-His 6-connecting peptide 2-guide protein-connecting peptide 3-protease cleavage site-PTH (1-34)/BL 21 (DE 3), is called pET28a-HSTP/BL21 (DE 3) for short, is selected. The amino acid sequence of the whole fusion protein is SEQ ID NO. 4.

EXAMPLE 3 bacterial disruption and treatment of inclusion bodies

Bacterial heavy suspension: and (3) carrying out high-density fermentation on the pET28a-PTH (1-34)/BL 21 escherichia coli engineering bacteria, and centrifugally collecting the bacteria for later use. About 50g of thallus is taken, and the weight (g) is as follows: volume (ml) ratio 1: mixing 5-10 ratio with PBS buffer solution (solution A) with pH of 6.0-8.5, suspending, and pre-cooling at 4deg.C.

High-pressure sterilization: and (3) flushing a pipeline of the high-pressure refiner by using distilled water, and starting a low-temperature circulation system for precooling to 1-4 ℃ for standby. Adding the precooled suspension bacteria liquid into a high-pressure refiner, maintaining the pressure at 60-80Mpa for 3-5 times, taking a smear crystal violet for dyeing, and taking less than 1-2 uncrushed bacteria under each view of an oil mirror as complete bacteria breaking.

High speed centrifugation: loading the liquid after bacteria breaking into a centrifugal barrel, centrifuging at 4 ℃ for 15-30min at 10,000-15,000g, and collecting the precipitate for standby.

Washing inclusion bodies: the solution A containing 0.5 to 1.5 percent of Triton X100 is adopted according to the weight percent: volume ratio 1: the inclusion body is resuspended in a proportion of 5-10, stirred by a magnetic stirrer for 15-30min, centrifuged for 15-30min at 10,000-15,000g, and the precipitate is collected for later use.

And (3) re-dissolving inclusion bodies: the solution A containing 8M urea is adopted according to the weight percentage: volume ratio 1: the inclusion bodies are resuspended in a proportion of 5-10, stirred by a magnetic stirrer for 15-30min, centrifuged for 15-30min at 10,000-15,000g, and the supernatant is collected for later use.

EXAMPLE 4 Ni-NTA affinity chromatography, TEV enzymatic cleavage and renaturation on column

Ni-NTA affinity chromatography packing is selected for preliminary purification, GST affinity packing is used for different types of products of different companies, in this example, ni-NTA affinity chromatography packing of the company invitrogen is used, and the wet weight of the bacterial cells per 100g packing is 10-20ml. After washing the filler with pure water for 2-5 volumes, balancing the filler with solution A containing 8M urea, mixing the dissolved inclusion body with the filler, gently mixing for 10-20min to remove unbound protein, and further removing impurity protein on the filler with solution A containing 20-25mM imidazole and 8M urea. Then adding a proper amount of TEV enzyme with His tag (about 0.1ml of enzyme is added into 1g of inclusion body) for enzyme digestion on a column, wherein the enzyme digestion liquid is A liquid containing 2M urea, the dosage of the enzyme digestion liquid is 1-2 times of that of the filler, the enzyme digestion condition is that the enzyme digestion is carried out at 4-25 ℃ for 2-5h, and the enzyme and the fusion protein are fully contacted by vertical suspension in the enzyme digestion process, so that the enzyme digestion is full, and the column renaturation is completed at the same time of enzyme digestion. After the cleavage, the supernatant was collected for subsequent purification.

EXAMPLE 5 cation exchange chromatography

Samples of affinity chromatography were collected, diluted 3-6 fold with solution B (20 mM PB, pH 6.5) and adjusted to pH around 6.5 for use. And (3) adopting a B solution equilibrium chromatography system and a 5ml SP HP chromatographic column, loading, and eluting unbound hybrid protein by using a solution A after loading. The solution C (20 mM PB,1M NaCl,pH6.5) is used for linear gradient elution, the elution flow rate is set to be 5ml/min, the elution gradient is from 0 to 50% of the solution B, the elution volume is 10 column volumes, finally 100% of the solution B is used for eluting impurities such as nucleic acid, and the eluted protein is collected and stored at 4 ℃ for standby. The chromatographic chart is shown in figure 2, wherein a small amount of hetero protein exists in the flow-through sample, two peaks are fused together during elution, and the peaks during elution are collected for subsequent purification.

Example 6: hydrophobic chromatography and displacement buffer

The sample obtained by the cation exchange chromatography is added with 3M ammonium sulfate solution until the final concentration of ammonium sulfate is 1-1.5M, a D solution (20 mM PB,1-1.5M ammonium sulfate, pH 6.5) is adopted to balance a chromatography system and a 5ml Phynel HP chromatographic column, then loading is carried out, and unbound hetero protein is eluted by the solution A after loading is finished. And (3) linearly gradient eluting with solution B, setting the eluting flow rate to be 5ml/min, wherein the eluting gradient is from 0 to 100% of solution B, the eluting volume is 10 column volumes, and collecting proteins for later use at 4 ℃. As shown in FIG. 3, the chromatographic chart shows two peaks at the time of elution, the front peak is the hetero protein, the rear peak is the target protein PTH (1-34), and the two peaks can be effectively separated.

The desalting was carried out by directly replacing the buffer solution with 50ml of G25 desalting column, using 200mM sodium acetate and 150mM NaCl as the buffer solution, sampling after desalting, performing SDS-PAGE identification, sub-packaging and freezing-storing the sample at-80. As shown in FIG. 4, the desalted sample has extremely high purity and no other hetero proteins are basically seen.

Example 7: HPLC detection

The purified PTH (1-34) protein was assayed for purity using a C18 column (available from Agilent corporation), the column was equilibrated with 0.1% TFA in water, 5ul of sample was loaded, 0.1% TFA in acetonitrile was eluted, the column temperature was set at 60℃and the flow rate was 0.5ml/min. The elution procedure was: 10-100% of B and 30min. The mass spectrum is shown in figure 5, and the result shows that the purity of PTH (1-34) is about 99%, and the purity requirement of biological products on protein medicines is met. Wherein, 0.1% TFA aqueous solution was prepared: water grade 1L I was mixed with 1ml TFA and filtered through a 0.22 μm filter. Preparation of 0.1% tfa acetonitrile solution: 1L acetonitrile was mixed with 1ml TFA.

Example 8: cell animals

1) Cell preparation: 2 bottles of Saos-2 cells were taken, medium was discarded, and each bottle was washed with 3ml PBS and discarded. Digestion was stopped by adding 1ml of pancreatin to each and then adding 5ml of incomplete medium. After all cells were removed by blowing with an elbow dropper, the liquid was transferred to a 15ml centrifuge tube, centrifuged at 1500 r.5 min, the supernatant was discarded, and 1ml of complete medium was added and mixed evenly for cell counting. After counting, the whole culture medium is used to prepare 2X 10 ⁵ 200 ul/well of 96 well plate, 37℃C, 5% CO ₂ Incubated overnight for about 28h.

(2) Preparation of PTH samples and culture medium: PTH samples were adjusted to 250ug/ml using sodium acetate buffer (pH 4.0). Complete medium (McCoy's medium+10% foetal calf serum+1% hepes) and live medium (0.1% bovine serum albumin plus complete medium to 10ml+0.5m ibmx+ corresponding protein sample) were prepared.

(3) Stimulation of cells and sample treatment: 8 EP tubes were taken, numbered 1-7. 180ul of the live medium was added to each of the 2-7 tubes. 312ul of the measurement medium was added to the 1-tube, and the volume to be added to the 1-tube was calculated after measuring the protein concentration so that the protein concentration in the 1-tube was 4000ng/ml. 60ul of the mixture is transferred from the tube 1 to the tube 2 for uniform mixing, the concentration is 1000ng/ml, 60ul of the mixture is transferred from the tube 2 to the tube 3 for uniform mixing, and the mixture is added into the tube 7. 7 holes are arranged on the cell plate, corresponding to the numbers 1-7, 150ul protein samples are added to each hole for stimulation, and the other hole is used as a cell blank for stimulation at 37 ℃ for 15min. Multiple wells were set up in the experiment and PTH standards purchased from Sigma were used as controls.

After the stimulation, the supernatant was aspirated, washed twice with 200ul PBS per well, and then 80ul of 0.1M HCL per well was placed at room temperature for 20Min. After completion, the cells were blown several times with a gun head, and 70ul of liquid was taken out from each well into the EP tube, and 70ul (0.5M PB solution+0.1M NaOH solution) was added to neutralize the pH to about 7.24. Centrifugation was performed at 1500rpm X10 min. This is the sample.

(4) ELISA procedure: the cAMP content in each stimulated sample was measured by competitive inhibition, which was performed strictly according to the instructions of the kit from cayman company.

The results show that: the PTH (1-34) purified by the scheme has biological activity of stimulating Saos-2 cells to generate cAMP, and the activity of the PTH is not lower than that of a standard product of Sigma company.

While the application has been described in detail with respect to the general description and specific embodiments thereof, it will be apparent to those skilled in the art that certain modifications and improvements may be made thereto based upon the application. Accordingly, such modifications or improvements may be made without departing from the spirit of the application and are intended to be within the scope of the invention as claimed.

Sequence listing

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Claims (8)

1. A method for the isolation and purification of recombinant parathyroid hormone PTH, said method comprising:

1) Bacterial disruption and inclusion body treatment

Homogenizing under high pressure, breaking bacteria, centrifuging at high speed, collecting precipitate, re-suspending and washing the precipitate, and mixing with the re-dissolving solution;

the compound solution is a mixed solution which takes solution A as a solvent and contains 8M urea, 6M guanidine hydrochloride or 2mol/L urea and sacosyl with the final concentration of 0.3 percent;

the solution A is PBS buffer solution with pH of 6.0-8.5;

the amino acid sequence of the recombinant parathyroid hormone PTH is SEQ ID NO 4;

the thalli are engineering bacteria of pET28a-PTH (1-34)/BL 21 escherichia coli;

2) Affinity chromatography; the filler is Ni-NTA;

3) Enzyme cutting and renaturation on the column:

wherein the enzyme is TEV enzyme;

4) Cation exchange chromatography and hydrophobic chromatography:

the stuffing of the cation exchange chromatographic column is selected from one of SP Sepharose HP, SP Sepharose FF, capto SP and Capto MMC;

the filler of the hydrophobic chromatographic column is selected from one of HP or FF fillers of Phynel, octyl or Butyl;

5) Desalting.

2. The method according to claim 1, wherein step 1) includes:

the weight of the thallus and the solution A is as follows: volume ratio 1: mixing at a ratio of 5-10, and pre-cooling to 1-4deg.C.

3. The method of claim 1, wherein step 1) comprises:

homogenizing at 1-4deg.C under 60-80Mpa for 3-5 times; centrifuging the liquid after bacteria breaking at 4 deg.C and 10,000-15,000g for 15-30min, and collecting precipitate for use.

4. The method of claim 1, wherein step 1) comprises:

re-suspending inclusion bodies in a re-suspension, the inclusion bodies and the weight of the re-suspension: the volume ratio is 1:5-10, stirring for 15-30min by a magnetic stirrer, centrifuging for 15-30min by 10,000-15,000g, and collecting precipitate for later use; the heavy suspension is solution A containing Triton X1000, tween20, tween80 or sacosyl with a final concentration of 0.5% -1.5%.

5. The method of claim 1, wherein step 1) comprises:

the weight is as follows: the volume ratio is 1: and 5-10 proportion of complex solution is added to resuspend the inclusion body, and after uniform mixing, the mixture is centrifuged and the supernatant is collected for standby.

6. The method of claim 1, wherein step 2) comprises:

the ratio of the wet weight of the bacterial cells to the filler is 10:1-2, mixing the re-dissolved inclusion body with the filler uniformly, and further removing the impurity protein on the filler by using solution A containing 20-25mM imidazole and 8M urea.

7. The method of claim 1, wherein step 3) comprises:

adding TEV enzyme on the affinity filler, performing enzyme digestion on the column, wherein the enzyme digestion liquid is A liquid containing 2-4M urea or guanidine hydrochloride, the dosage of the enzyme digestion liquid is 1-2 times of that of the filler, and the enzyme digestion condition is 4-25 ℃ for enzyme digestion for 2-5 hours; wherein, the weight-volume ratio of the inclusion body to the enzyme is 10 in terms of g: ml: 1.

8. the method of claim 1, wherein said step 5) comprises:

the desalting is achieved by one selected from ultrafiltration, diafiltration, molecular sieves or desalting columns.

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