Corynebacterium glutamicum ATCC 31831 grew on L-arabinose as the sole carbon source at a specific growth rate twice that on D-glucose. The gene cluster responsible for L-arabinose utilization comprised a six cistron transcriptional unit with a total length of 7.8-kb. Three L-arabinose-catabolizing genes, araA (encoding L-arabinose isomerase), araB (L-ribulokinase) and araD (L-ribulose-5-phosphate 4-epimerase) comprised the araBDA operon, upstream of which three other genes, araR (LacI-type transcriptional regulator), araE (L-arabinose transporter) and galM (putative aldose 1-epimerase) were present in divergent orientation. Inactivation of araA, araB or araD genes abolished growth on L-arabinose and each of the gene products was functionally homologous to their E. coli counterpart. Moreover, when compared to the wild type strain, an araE disruptant exhibited a greater than 80% decrease in growth rate at lower (3.6 g l(-1)) but not at higher (40 g l(-1)) concentrations of L-arabinose. The expression of araBDA operon and araE gene was L-arabinose-inducible and negatively regulated by transcriptional regulator AraR. Disruption of araR abolished the repression in the absence of L-arabinose. Expression of the regulon was not repressed by D-glucose, and simultaneous utilization of L-arabinose and D-glucose was observed in aerobically growing wild type and araR deletion mutant cells. The regulatory mechanism of the L-arabinose regulon is, therefore, distinct from carbon catabolite repression in other bacteria.