Structure and function of the serine pathway enzymes in Hyphomicrobium

Abstract

A certain group of methylotrophic bacteria possess the serine pathway for the assimilation of C1 compounds, and this pathway operates to synthesize 2- phosphoglycerate as a precursor of cell constituents, comprising the following two part. In the first part, 2-phosphoglycerate is synthesized from glyoxylate and formaldehyde, and malyl-CoA is also formed by subsequent enzyme reactions. In the second part of the pathway, malyl-CoA is cleaved to glyoxylate and acetyl-CoA, and another molecule of glyoxylate is generated from acetyl-CoA. Two variants of the serine pathway have been reported (C. Anthony, 1982), in which the route for the generation of glyoxylate from acetyl-CoA is varied. In the icl +-serine pathway, isocitrate lyase is involved in the route of the oxidation of acetyl-CoA to glyoxylate. Another variant, icl --serine pathway, is known in methylotrophic bacteria such as Methylobacterium and Hyphomicrobium strains (C. Anthony, 1982), which have no isocitrate lyase activities, and the route for the generation of glyoxylate has not been elucidated.