Journal Article

PreJuSER-24490

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Identification of glyA (serine hydroxymethyltransferase) and its use together with the exporter ThrE to increase L-threonine accumulation with Corynebacterium glutamicum

Simic, P.FZJ* ; Willuhn, J. ; Sahm, H.FZJ* ; Eggeling, L.FZJ*

2002
Soc. Washington, DC [u.a.]

This record in other databases:      

Please use a persistent id in citations: http://hdl.handle.net/2128/2410  doi:10.1128/AEM.68.7.3321-3327.2002

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 mumol 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 chromosome under the control of P-tac, making glyA expression isopropylthiogalactopyranoside dependent. In this way, the SHMT activity in an L-threonine producer was reduced to 8% of the initial activity, which led to a 41% reduction in glycine, while L-threonine was simultaneously increased by 49%. The intracellular availability Of L-threonine to aldole cleavage was also reduced by overexpressing the L-threonine exporter thrE. In C glutamicum DR-17, which overexpresses thrE, accumulation of 67 mM instead of 49 mM L-threonine was obtained. This shows that the potential for amino acid formation can be considerably improved by reducing its intracellular degradation and increasing its export.

Keyword(s): J

Note: Record converted from VDB: 12.11.2012

---

Contributing Institute(s):

1. Biotechnologie 1 (IBT-1)

Research Program(s):

1. Biotechnologie (L02)

Appears in the scientific report 2002

---

Database coverage:

---