Methanol Assimilation by Hyphomicrobium sp.

Abstract

Summary: A study has been made in methanol- and ethanol-grown Hyphomicrobium x of the specific activities of the following enzymes: serine hydroxymethyltransferase, serine-glyoxylate aminotransferase, hydroxypyruvate reductase, glycerate kinase, phosphopyruvate hydratase, phosphopyruvate carboxylase, serine dehydratase, malate dehydrogenase (decarboxylating), phosphopyruvate synthase, phosphopyruvate carboxykinase, glycerate phosphomutase, malate dehydrogenase, malate lyase (CoA acetylating-ATP cleaving), citrate synthase, aconitate hydratase, isocitrate lyase and malate synthase. It was concluded that during growth on ethanol the glyoxylate cycle operated, while during growth on methanol, C1 units and glyoxylate were converted to malate by the serine pathway. The glyoxylate was regenerated by cleavage of malate into glyoxylate and acetyl-CoA. The acetyl-CoA was itself oxidized to glyoxylate by some of the reactions of the tricarboxylic acid cycle and isocitrate lyase, thus permitting net synthesis of C3 and C4 compounds from methanol and carbon dioxide.