d-Allose Catabolism of Escherichia coli: Involvement of alsI and Regulation of als Regulon Expression by Allose and Ribose

Genes involved in allose utilization of Escherichia coli K-12 are organized in at least two operons, alsRBACE and alsI, located next to each other on the chromosome but divergently transcribed. Mutants defective in alsI (allose 6-phosphate isomerase gene) and alsE (allulose 6-phosphate epimerase gene) were Als(−). Transcription of the two allose operons, measured as β-galactosidase activity specified by alsI-lacZ(+) or alsE-lacZ(+) operon fusions, was induced by allose. Ribose also caused derepression of expression of the regulon under conditions in which ribose phosphate catabolism was impaired.