Identification of glyA (encoding serine hydroxymethyltransferase) and its use together with the exporter ThrE to increase L-threonine accumulation by Corynebacterium glutamicum.

ABSTRACT: L-threonine can be made by the amino acid-producing bacterium Corynebacterium glutamicum. However, in the course of this process, some of the L-threonine is degraded to glycine. We detected an aldole cleavage activity of L-threonine in crude extracts with an activity of 2.2 nmol min(-1) (mg of protein)(-1). In order to discover the molecular reason for this activity, we cloned glyA, encoding serine hydroxymethyltransferase (SHMT). By using affinity-tagged glyA, SHMT was isolated and its substrate specificity was determined. The aldole cleavage activity of purified SHMT with L-threonine as the substrate was 1.3 micromol min(-1) (mg of protein)(-1), which was 4% of that with L-serine as substrate. Reduction of SHMT activity in vivo was obtained by placing the essential glyA gene in the chrom

SUBMITTER: Simic P 

PROVIDER: S-EPMC126772 | biostudies-literature | 2002 Jul

REPOSITORIES: biostudies-literature