Normal 2-aminobutyrate oxidation and increased valine oxidation in fibroblasts deficient in pyruvate dehydrogenase

Human skin fibroblasts deficient in pyruvate dehydrogenase and five normal control strains were incubated with one of the following labelled substrates: DL-[1-14C]-2-amino-n-butyric acid, DL-[3-14C]-2-amino-n-butyric acid, L-[1-14C]leucine, L-[1-14C]valine, L-[1-14C]alanine, and [1-14C]pyruvate. The rate of 14CO2-production in the deficient cells was normal from 2-aminobutyrate and leucine, increased from valine, and decreased from alanine and pyruvate. These results indicated that in human skin fibroblasts the decarboxylation of 2-oxobutyrate is catalysed by an enzyme system different from the pyruvate dehydrogenase complex.