Summary: mutants relieved of carbon repression were isolated from an parental strain by selection of colonies that exhibited improved growth on a combination of 4-aminobutanoic acid (GABA) and D-glucose. In addition to derepression of the utilization of GABA as a nitrogen source in the presence of D-glucose, three of the four mutants also showed derepression of L-alanine and L-proline utilization. Transformation of the mutants with the gene, encoding the repressor protein CREA, re-established the phenotype on GABA/D-glucose, identifying the mutations as . The gene mapped on chromosome IV by linkage analysis and contour-clamped homogeneous electric field hybridization. The mutants obtained were used to study the involvement of CREA in repression by D-glucose of arabinases and L-arabinose catabolism in . In wild-type , α-L-arabinofuranosidase A, α-L-arabinofuranosidase B, endo-arabinase, L-arabinose reductase and L-arabitol dehydrogenase were induced on L-arabinose, but addition of D-glucose prevented this induction. Repression was relieved to varying degrees in the mutants, showing that biosynthesis of arabinases and L-arabinose catabolic enzymes is under control of CREA.


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