Studies on vitamin B6 metabolism in microorganisms. Part XX. Vitamin B6 biosynthesis of a Pdx mutant,Escherichia coli B WG3,in amino acid-supplemented medium.

Abstract

Alanine, cystine, cysteine, β-hydroxypyruvate, an amino acid mixture and glycolaldehyde, which were found to satisfy the vitamin B6 (B6) requirement of Escherichia coli B WG3, a pdxB mutant, by paper disc assay method, were examined about the effect on growth of the mutant in liquid cultivation. Alanine and β-hydroxypyruvate did not significantly affected growth under the culture conditions, whereas cysteine and cystine supported growth to some extent. The amount of B6 synthesized by the mutant in the amino acid-supplemented medium was from 0.05 to 0.12 nmol per ml. The amount of B6 synthesized in the medium, which was supplemented with an amino acid mixture composed of l-cysteine, l-threonine and l-methionine, was about 0.15 nmol per ml. This amount of B6 was lower than the amount (0.4 nmol per ml) biosynthesized in glycolaldehyde-supplemented medium. The data suggested that growth of the mutant supplemented with amino acids could not be supported by only the B6 biosynthesized from them, because such amo...