Expression, purification and characterization of rat procarboxypeptidase B in Pichia pastoris / 生物工程学报

Carboxypeptidase B is a metalloenzyme, which is widely used for commercial and research purposes. Commercially available CPB purified from porcine or bovine pancreas is very expensive, and is not totally free from other proteases. In order to express the rat proCPB in Pichia pastoris, total RNA extracted from SD rat pancreas cells was reversely transcripted to synthesize cDNA, and the proCPB ORF was synthesized by PCR. After digestion with Xho I and EcoR I , the fragment was inserted into pPIC9, and the recombinant plasmid was named as pPIC9-proCPB. By digestion with Sac I , the lined pPIC9-proCPB was transformed into Pichia pastoris strains GS115 with PEG1000 and integrated into their genomes. In the inducement of methanol, recombinant proCPB was successfully expressed in Pichia pastoris, and could be secreted into the supernatant in the culture. After optimizing the fermentation conditions, a higher production could be obtained when GS115-proCPB was induced in BMGY (pH6.0) at 28CC, with addition of 0.5% casein. The yield of recombinant protein reached 500mg/L, achieving over 94% of total protein in the culture supernatant. The purity of recombinant CPB can reach 96% after two step phenyl sepharose F F purification, and 38% of total protein can obtained after optimizing the pufication method. Comparing to the specific activity 180u/mg of CPB purchased from Sigma, the specific activity of recombinant CPB is 110u/mg. Mass spectrometry analyses showed the mass of the recombinant CPB was 35.1 kD, which is very close to the theory value 35.2 kD. Amino acid sequencing of N-terminal of recombinant CPB further indicated proCPB was expressed successfully and modificated correctly after translation.

Recombinant batroxobin expressed highly in Pichia pastoris / 生物工程学报

Methylotrophic yeast, Pichia pastoris was used to express recombinant batroxobin, and a technology route of producing recombinant protein was finally established. We synthesized batroxobin gene artificially by means of recursive PCR. pPIC9-batroxobin was constructed and transformed into Pichia pastoris GS115 (his4). Recombinant batroxobin was expressed in yeast engineering strain and it was purified from the culture supernatant. 10 mg of recombinant batroxobin was purified from 1 liter fermentation media, it exhibited specific activity of 238 NIH units/mg and had molecular weight of 30.55 kD. The purified recombinant protein converted fibrinogen into fibrin clot in vitro, and shortened bleeding time in vivo. This study laid a foundation of development of hemostatic of recombinant snake venom thrombin-like enzyme.

Expression of fusion protein of parathyroid hormone and transferrin N-terminal half-molecule in Pichia pastoris / 生物工程学报

The fused gene (PTH-TFN) of parathyroid hormone (PTH) gene and transferring N-terminal half-molecule (TFN) gene was amplified by multiple PCR and inserted into pPIC9 vector. The recombinant plasmid pPIC9-PTH-TFN was transformed into Pichia pastoris GS115 by PEG. After methanol induction, the target protein was expressed in fermentation supernatant at high level. The fused protein PTH-TFN with purity being higher than 95% was finally obtained after purification through two-step chromatography: SP Sepharose Fast Flow and Phenyl Sepharose Fast Flow. Western blot analysis and adenylate cyclase assay proved that the fused protein exhibited the bioactivity to stimulate cAMP synthesis and the ability to bind Fe3+ in the Fe3+ saturation study as the recombinant TFN did indicating that TFN could be used as the transcellar carrier of PTH.

Expression and bioactive characterization of bacteriophage lysin gene of Bacillus anthracis in Escherichia coli / 生物工程学报

The lysin gene of Bacillus anthracis-diagnosing bacteriophage, obtained by PCR amplification,was cloned into the Escherichia coli exepression vector pET22b which has been cleaved by EcoR I and Nde I. The recombinant vector pET22b-gamma lysin was verified to be correctly constructed by PCR, sequencing and enzyme digestion, and highly expressed in E. coli BL21 (DE3), which accounted for about 40 percent of total protein in E. coli BL21 (DE3), while in the 5L fermentor the expression level reached 15g/L. After expression, disruption and purification with three-step chromatography, Streamline SP, SP HP and Sephacryl S-100, the recombinant gamma lysin was finally obtained with purity of higher than 95 percent as determined by gel scan. The final yield following SP HP was 19.1 percent, with a greater-than-350-fold increase in specific activity. The pure enzyme has been shown active to Bacillus anthracis, and not to E. coli, Bacillus subtilis and Bacillus cereus. Its specific activity was about 1400 u/mg.

High expression and characterization of human parathyroid hormone in Escherichia coli / 生物工程学报

Human parathyroid hormone (hPTH) was highly expressed in Escherichia coli by inserted the synthesized whole hPTH cDNA into the vectors pBV220 and pET22b. After expression and disruption, the purified product was acquired through cation exchange chromatography and reverse phase chromatography. From the results of N-terminal sequencing and MALDI-TOF-MS analysis the recombiant prtein was indentified as intact hPTH. In in vitro Bioassays the recombinant hPTH stimulated adenylate cyclase as the standard did. In ovariectomized rats the recombinant hPTH markedly increased the femoral bone mass and bone mineral density.