The Purification and Properties of Cytidine Diphosphate

Crude extracts of Salmonella fyphi catalyze the conversion of cytidine diphosphate D-glucose to CDP-tyvelose. Two intermediates in this reaction sequence have been identitied as CDP-4-keto-6-deoxyglucose and CDP-paratose. The enzyme catalyzing the conversion of CDP-D-glucose to CDP-4-keto-6-deoxyglucose (CDP-n-glucose oxidoreductase) has been purified approximately 50-fold from these extracts, and its properties have been studied. The product of the reaction, CDP-4-keto-6-deoxy-n-glucose, was characterized by chemical reduction. Mild acid hydrolysis of the reduced nucleotide yielded two 6-deoxyhexoses which were identified as D-fucose (6-deoxygalactose) and 6-deoxyD-glucose by chromatographic, chemical, and enzymatic methods CDP-D-glucose oxidoreductase has been shown to require nicotinamide adenine dinucleotide. The enzyme was not activated by NADP+. However, the over-all reaction from CDP-D-ghrcose to CDP-tyvelose has been shown to require NADPH, indicating that this cofactor is involved at a later step in the reaction sequence.