Methionine synthesis by extracts of Salmonella typhimurium

Abstract

Following the genetic studies by Smith (1961) and Smith and Childs (1963) with methionine auxotrophs of Salmonella typhimurium, methionine formation from homocysteine has been investigated with cell-free extracts of this organism. As found with Escherichia coli (Woods, Foster and Guest, 1964), methyl groups are formed by an N5N10-methyl-enetetrahydrofolate reductase. They are then transferred to homocysteine by either a simple N5-methyltetrahydropteroyltriglutamate-honocysteine methyltransferase or alternatively a cobalamin-dependent N5-methyltetrahydrofolate-homocysteine methyltransferase; S. typhimurium differs from E. coli in being able to synthesize significant amounts of cobalamin.