The conversion of leucine to α-ketoisocaproic acid and its metabolic consequences for Escherichia coli K12

Abstract

The amino acid L-leucine serves as a good auxiliary nitrogen source for Escherichia coli K12, and in so doing is converted to alpha-ketoisocaproic acid which is excreted into the medium.L-Leucine does not serve as sole nitrogen source. Cells incubated with L-leucine as sole nitrogen source do not grow, although they do metabolize leucine, and accumulate ketoisocaproic acid in the medium.Where glycine is the only other nitrogen source, the presence of L-leucine greatly increases the growth rate even at concentrations so low that its contribution as nitrogen donor is unlikely to be important.