Catabolism of d-Glucaric Acid to α-Ketoglutarate in Bacillus megaterium

摘要

Crude cell-free extracts of d-glucarate-grown cells of Bacillus megaterium converted d-glucarate to α-keto-β-deoxy-d-glucarate (KDG). Charcoal-treated cell-free extracts or partially purified enzyme preparations converted KDG to an intermediate which was isolated and identified as 2,5-diketoadipate (DKA). This compound was synthesized, and the cell-free extracts of d-glucarate grown cells were found to catalyze the reduction of nicotinamide adenine dinucleotide (NAD) in its presence. In the absence of NAD, the same enzyme preparation catalyzed the decarboxylation of the DKA to α-ketoglutarate semialdehyde (KGS), whereas in the presence of NAD the KGS was subsequently oxidized to α-ketoglutarate by α-ketoglutarate semialdehyde dehydrogenase. Since galactarate-grown B. megaterium contains a galactarate dehydrase forming KDG, the complete pathway for the metabolism of d-glucarate or galactarate to α-ketoglutarate and CO2 is now known in a gram-positive bacterium.