Characterization of a novel serine hydroxymethyltransferase isolated from marine bacterium Arthrobacter sp. and its application on L-serine production.

The current L-serine production relies mainly on cellular or enzymatic conversion from the precursor glycine plus a C1 compound. To date, only several reports have been published on L-serine production from glycine and methanol by methylotrophic bacteria with the serine pathway. This work aimed to isolate a novel serine hydroxymethyltransferase (SHMT) from the methanol-using Arthrobacter sp. and use it for L-serine production with the enzymatic conversion method. Here, A novel glyA gene was isolated from the methanol-using Arthrobacter sp. by thermal asymmetric interlaced PCR (TAIL-PCR), encoding a serine hydroxymethyltransferase (SHMT) with 440 amino acids, belonging to the α-family of fold type I, and pyridoxal-5-phosphate (PLP) dependent enzymes. The enzyme was stable in weakly alkali conditions, showing the optimal activity at pH 7.8 and 45 °C, and a 2.75-fold increase in activity over the corresponding enzyme of Escherichia coli. Two methods (resting cells reaction and enzymatic conversion) were employed to produce serine. Using glycine (133 mM) and formaldehyde (13.3 mM) as substrates to produce serine by enzymatic reaction, 93.6 mM L-serine was obtained with a 70.4 % molar conversion rate from glycine to L-serine. Thus, the characteristics of this novel strain and its enzyme suggest that it has the potential for further research and industrial use.