Membrane-boundd-Gluconate Dehydrogenase ofSerratia marcescens: Purification and Properties

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Abstract
Membrane-bound d-gluconate dehydrogenase, which catalyzes oxidation of d-gluconate to 2-keto-d-gluconate in the presence of an electron transport system, was purified to homogeneous state from Serratia marcescens IFO 3054. Purification was achieved at about 450-fold with an overall yield of 18% from the particulate fraction by solubilization with Triton X-100, subsequent fractionations on DEAE-cellulose and DEAE-Sephadex column chromatographies, and precipitation with polyethylene glycol 6000. The purified enzyme preparation was found to be an enzyme-cytochrome complex and the dehydrogenase protein tightly bound cytochrome c1 component which had the absorption maxima at 418, 523 and 554 nm. The substrate specificity of the enzyme seemed to be restricted to only d-gluconate and the apparent Km value of the purified enzyme for d-gluconate was 0.8 × 10-3 m. Enzyme activity was inhibited by pyruvate competitively and by oxamate noncompetitively.