1887

Abstract

SUMMARY: Washed suspensions of two strains of which require vitamin B for growth form methionine in a reaction mixture containing homo-cysteine, serine, glucose, -aminobenzoic acid and cobalamin only when pyridoxal or another member of the vitamin B group (except pyridoxamine phosphate) is also added.

Serine is replaced by glycine as donor of the required one-carbon unit, but the activity of glycine is markedly increased when the organism is harvested from a medium containing glycine. Pyridoxal is not required for the utilization of glycine by such organisms, but is essential when glycine has not been present during growth. It is concluded that growth on glycine induces the formation of an alternative, and more efficient, mechanism for using glycine as one-carbon donor which is independent of pyridoxal. This mechanism was studied in suspensions of an auxotroph requiring serine or glycine for growth by isotopic technique; C-2 of glycine is incorporated into the niethyl group of methionine at four times the activity at which it appears in a serine pool. Free serine is therefore not an intermediate in the utilization of glycine as a one-carbon donor. Cobalamin is required for maximal activity of both glycine and serine in the reaction.

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/content/journal/micro/10.1099/00221287-22-3-786
1960-06-01
2019-10-22
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