3-Ketoglucose Reductase of Agrobacterium tumefaciens

Two kinds of 3-ketoglucose-reducing enzyme were partially purified from the sonic extract ofAgrobacterium tumefaciens IAM 1525 grown on a sucrose-containing medium. Both enzymes have a specific requirement for reduced nicotinamide adenine dinucleotide phosphate (NADPH) as a hydrogen donor and catalyze the reduction of 3-ketoglucose to glucose but do not reduce 3-ketoglucosides such as 3-ketosucrose, 3-ketoglucose-1-phosphate, 3-ketotrehalose, and 3-ketocellobiose. From the requirement and substrate specificity of the enzymes, the name NADPH:3-ketoglucose oxidoreductase (trivial name, 3-ketoglucose reductase) was proposed. By diethylaminoethyl-cellulose column chromatography, two reductases were separated, and the early and late eluted enzymes were designated reductase I and II, respectively.K m values of reductase I and II were as follows: for 3-ketoglucose both had an identical value of 2.5 × 10−5 m , and for NADPH the values were 1.0 × 10−5 m and 1.5 × 10−5 m , respectively. Optimalp H values were also identical:p H 4.8 to 5.0 in 10−2 m phosphate buffer. Intracellular localization of the enzymes is discussed.