Metabolism of d-Arabinose by Aerobacter aerogenes: Purification of the Isomerasea
AUTOR(ES)
Oliver, Eugene J.
RESUMO
In Aerobacter aerogenes, the mutational event permitting the utilization of d-arabinose as a source of carbon and energy is a regulatory mutation resulting in the constitutive synthesis of certain enzymes of the l-fucose catabolic pathway. l-Fucose isomerase catalyzes the isomerization of d-arabinose to d-ribulose. This enzyme was purified to homogeneity as indicated by a single band in disc-gel electrophoretic columns and single peaks with column chromatography and ultracentrifugation from the wild-type PRL-R3 strain, induced with l-fucose and two constitutive mutants, 502 and 510. The ratios of the activities of this isomerase on d-arabinose and l-fucose remained constant throughout all purifications. The apparent Km of the isomerase from the wild-type strain induced with l-fucose and from the constitutive mutant strains was 5.0 × 10−2m for l-fucose and 1.5 × 10−1m for d-arabinose. A strain 531 possessing an apparent alteration in the isomerase was isolated from the strain 502. This altered isomerase exhibited a lowered Km for d-arabinose.
