ABSTRACT
A new fusion expression vector, pED-P8-Hi-lys was designed and constructed. It includes four parts, a 20 peptide sequence of hirudin that can maintain anticoagulant activity, the C-terminus of asparaginase as a fusion partner, basic octopeptide (KRKRKKSR) that makes the fusion partner easy to remove, and the unique acid-labile aspartyl-prolyl bond. It was transformed into E. coli BL-21 and the fusion protein (AnsB-C-P8-Hi-lys) was expressed effectively as inclusion bodies after inducing by lactose. The objective peptide Hi-lys was purified by means of cell disruption, washing, ethanol precipitation, acid hydrolysis, and DEAE-cellulose 52 column chromatography. The antithrombin activity of the purified Hi-lys peptide was about 50 ATU/mg by thrombin activity assays.
ABSTRACT
Purpose The aim is to optimize the liquid culture conditions of dihydropyrimidinase producing strain Pseudomonas putida 9801. Methods Plackett-Burman design and spherical symmetric desig n were used.Results Optimum conditions for dihydropyrimidinas e formation of Pseudomonas putida 9801 were defined:yeast extract 2.39%, Glu cose 1.81%,Uracil 0.06%,K2HPO4*3H2O 0.2%, MgCl2*6H2O 0.05%and NaCl 0 .3%,when the strain was cultured at 32℃ for 10 h,about 3.02 units/ml of hydanto inase was obtained. This value was quite consistent with the theory value(2.91 u nits/ml).Conclusion The liquid culture conditions of dihydrop yrimidinase producing strain were optimized.
ABSTRACT
AIM The purpose is to construct D-hydantoinase genetic engineering strain for the purpose of the industrial production of D-p-hydroxyphenylglycine. METHODS D-hydantoinase gene was created from Pseudomonas putida 9801 by PCR technique and inserted into pMD18-T vector. The recombinant plasmid was transformed into several Escherichia coli strains. The positive transformants with D-hydantoinase activity were obtained by the two step screening, digoxigenin DNA labeling in situ hybridization and D-hydantoinase activity assay. RESULTS The D-hydantoinase activity of the genetic engineering strain E.coli BL21/pMD-dht was 1700 U*L-1 and increased as high as 8 times compared with those of wild-type strain Pseudomonas putida 9801. The subunit molecular weight of recombinant D-hydantoinase was about 53 kDa measured by SDS-PAGE. The amount of the recombinant D-hydantoinase was about 20 percent of total bacterial soluble proteins. CONCLUSION The genetic engineering strain E.coli BL21/pMD-dht possesses the initial industrial production prospects.