Crude cell-free extracts of D-glucarate-grown cells of Bacillus megaterium converted D-glucarate to a-keto-fl-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 dirrucleotide (NAD) in its presence. In the

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... sence of NAD, the same enzyme preparation catalyzed the decarboxylation of the DKA to a-ketoglutarate semialdehyde (KGS), whereas in the presence of NAD the KGS was subsequently oxidized to a-ketoglutarate by a-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 a-ketoglutarate and CO2 is now known in a gram-positive bacterium.