Production of l-serine from glycine by Corynebacterium glycinophilum and properties of serine hydroxymethyltransferase, a key enzyme in l-serine production

Abstract

Fermentative production of l-serine from glycine by Corynebacterium glycinophilum AJ-3413, an auxotrophic mutant of Leu and Met with increased productivity of l-serine using a one liter jar fermentor was carried out and the properties of serine hydroxymethyltransferase (SHMT), a key enzyme in l-serine synthesis, of the parental strain AJ-3170 were investigated. SHMT was effectively induced by the addition of glycine to the medium at an early stage of cultivation. Under optimal conditions, AJ-3413 produced 16.0 g/ l of l-serine from 30 g/ l of glycine with a molar yield of 38%. The partially purified SHMT catalyzed the l- allo-threonine degradation in addition to l-serine degradation, but could not catalyze l-threonine degradation. This enzyme showed an absolute tetrahydrofolic acid requirement for l-serine degradation to glycine and formaldehyde, but not for l- allo-threonine degradation. Pyridoxal 5′-phosphate appeared to be required for enzyme activity. The K m values for glycine and formaldehyde in l-serine synthesis, and for l-serine in l-serine degradation were 1.85, 0.29 and 1.64 mM, respectively.