d-Glucaric Acid and Galactaric Acid Catabolism by Agrobacterium tumefaciens

Cell-free extract (crude extract) of Agrobacterium tumefaciens grown on d -glucuronate or d -glucarate converts d -glucarate and galactarate to a mixture of 2-keto-3-deoxy- and 4-deoxy-5-keto- d -glucarate. These compounds are then converted by partially purified crude extract to an intermediate tentatively identified as 2,5-diketoadipate. The same enzyme preparation further decarboxylates this intermediate to α-ketoglutarate semialdehyde, which is subsequently oxidized in a nicotinamide adenine dinucleotide-dependent reaction to α-ketoglutaric acid. Since A. tumefaciens converts d -glucuronic acid to d -glucarate, a pathway from d -glucuronate to α-ketoglutarate in A. tumefaciens was determined.