METHIONINE BIOSYNTHESIS IN ESCHERICHIA COLI

The first nonsulfur containing compound implicated in the biosynthesis of the amino acid methionine in microorganism was reported by Teas et al. (1948). These investigators found that a single amino acid, -homoserine, would support the growth of a biochemical mutant of Neurospora crassa which required both methionine and threonine for growth. They concluded that L-homoserine condensed with cysteine to form cystathionine which then underwent cleavage to yield homocysteine, the immediate precursor of methionine, as shown in the following scheme: of similar experiments involving biochemical mutants of Escherichia coli (Simmonds, 1948; Gots and Koh, 1950; Davis and Mingioli, 1950) are in accord with the scheme for Neurospora shown above. The present paper reports the results of a study of the pathway of methionine formation in mutants of E. coli which require methionine for growth. The results of this study are in harmony with the existing scheme for the biosynthesis of methionine in E. coli but in addition implicate other nonsulfur containing amino acids beside

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