Characterization of a serine hydroxymethyltransferase for l-serine enzymatic production from Pseudomonas plecoglossicida

Pseudomonas plecoglossicida, a bacterium strain that exhibits high Serine hydroxymethyltransferase (SHMT) activity, was isolated from the seawater. A full-length glyA encoding SHMT was obtained by a modified thermal asymmetric interlaced-PCR (TRIL-PCR), which consisted of 1,254 bp, encoded a 417 amino acid polypeptide, and shared the highest identity (75 %) with a glyA gene from Acinetobacter radioresistens CMC-1. Recombinant glyA gene was expressed in Escherichia coli BL21 (DE3) and purified by electrophoretic homogeneity. The enzyme showed the optimal activity at pH 8.0 and 40 A degrees C, and remained stable in high alkali conditions. Using SHMT to produce l-serine by catalyzing the reaction of glycine and tetrahydrofolate is one of the most promising routes to synthesize l-serine, achieving 33.4 mM l-serine at the 12th h of the enzymatic reaction with the substrates of glycine (133 mM) and formaldehyde (13.3 mM). The properties make the SHMT a candidate for further enzymatic studies and industrial applications.