A novel serine hydroxymethyltransferase from Arthrobacter nicotianae: characterization and improving catalytic efficiency by rational design

BACKGROUND Serine hydroxymethyltransferase (SHMT) is the key enzyme in L-serine enzymatic production, suggesting the importance of obtaining a SHMT with high activity. RESULTS Here, a novel SHMT gene, glyA, was obtained through degenerate oligonucleotide-primed PCR and encoded a novel SHMT with 54.3% similarity to the known SHMT from Escherichia coli. The obtained protein AnSHMT showed the optimal activity at 40 °C and pH 7.5, and was more stable in weakly alkali conditions (pH 6.5-8.5) than Hyphomicrobium methylovorum's SHMT (pH 6.0-7.5), In order to improve the catalytic efficiency of the wild type, the site-directed mutagenesis based on sequences alignment and bioinformatics prediction, was used and the catalytic efficiency of the mutant I249L was found to be 2.78-fold higher than that of the wild-type, with the replacement of isoleucine by leucine at the 249 position. CONCLUSIONS This research provides useful information about the interesting site, and the application of DOP-PCR in cloning a novel glyA gene.