The synthesis and function analysis of omega-3 fatty acid desaturase gene from Caenorhabditis briggssae / 生物工程学报

Omega-3 polyunsaturated fatty acids (PUFAs) have been broadly investigated and shown to exert many preventive and therapeutic actions besides their important role in maintenances human health and normal development. In mammals, the level of omega-3 PUFAs is relatively too low compared with omega-6 PUFAs, which metabolically and functionally distinct from omega-3 PUFAs and often have important opposing physiological functions. Either the inefficiency of omega-3 PUFAs or the excess of omega-6 PUFAs will cause many healthy problems. So methods have been sought to increase the amount of omega-3 PUFAs and to improve the omega-6/omega-3 ratio in body. In this study, the sFat-1 gene, which putatively encodes a omega-3 fatty acid desaturase, was chemically synthesized according to the sequence from Caenorhabditis briggssae (with codon usage modified), and constructed into a mammal expression vector pcDNA3. 1-sFat1-EGFP. This vector was introduced into CHO cells by lipid-mediated transfection, and it's expression quickly and effectively elevated the cellular omega-3 PUFAs (from 18-carbon to 22-carbon) contents and dramatically improved the ratio of omega-6/omega-3 PUFAs. Cellular lipids extracts from stably selected cells were analyzed with GC-MS and the results showed that amount of total omega-6 PUFAs dropped from 48.97% (in GFP cells)to 35.29% (in sFat-1 cells), whereas the amount of total omega-3 PUFAs increased from 7.86% to 24.02%, respectively. The omega-6/omega-3 ratio also dropped from 6.23 to 1.47. These data demonstrates the Caenorhabditis briggssae omega-3 Fatty Acid Desaturase gene, sFat-1, was synthesized successfully and can produce omega-3 PUFAs by using the corresponding omega-6 PUFAs as substrates, which shows its potential for use in the production of omega-3 PUFAs in transgenic animals.

The construction and characterization of human pro-urokinase mutant / 生物工程学报

It is very easy for the pro-UK to lose it's biological activity because of the digestion of pro-UK by the thrombin or the inhibition of pro-UK by the PAI-I. So three pro-UK mutant (pro-UK) genes were constructed in this experiment with the PCR point-mutant method. The thrombin cleavage site Arg156 in pro-UK was mutated into His156, and named as pro-UKM1; PAI binding sites Arg178, Arg179, Arg181 were mutated into Lys178, Lys179, His181, named as pro-UKM2; The mutant containing His156, Lys178, Lys179, His181 as pro-UKM3. Three mutants were expressed in CHO cells respectively and analyzed with SDS-PAGE fibrin plate assay and western blot. The results showed that the three mutants and the native pro-UK have the same single electrophoresis band indicating most of the pro-UK was single chain. In vitro plasma clot lysis assays indicated that the pro-UKM1 have the ability to resistant against thrombin digestion; pro-UK2 could resist against PAI inhibition; while pro-UK3 improved resistances against both thrombin and PAI. It looks very promising that the pro-UK3 can be a new medicine of dissolving thrombus.