α-KETOISOVALERIC ACID, A PRECURSOR OF PANTOTHENIC ACID IN ESCHERICHIA COLI

Abstract

The synthesis of pantoic acid in Escherichia coli and Aerobacter aerogenes proceeds via a-oxoiso-valeric acid (oxovaline) and a-oxo-b, b-dimethyl-g-hydroxy-butyric acid (oxopantoic acid). Thus, oxovaline is a common precursor of valine and pantothenic acid. This is indicated by the following facts. Cell suspensions of wild type Escherichia coli, in the presence of glucose, synthesize pantoate; a strain blocked between oxovaline and valine also does so, but a strain blocked before oxovaline does not, unless either oxovaline or oxopantoate is supplied. A pantoate-requiring mutant of E. coli, when growing on a limiting supplement of pantoate, excretes valine which is presumed to be formed from oxovaline, known to be a normal precursor of valine. A mutant of Aerobacter aerogenes was found to grow, though slowly, on any of the following supplements; valine, oxovaline, oxopantoate, pantoate, pantothenate. Growth inhibition of E. coli by salicylate, known to be reversible by pantoate, is also reversible by oxovaline and oxopantoate. [on SciFinder (R)]