title: Stereochemistry of the hydrogen transfer to NAD catalyzed by D-galactose dehydrogenase from Pseudomonas fluorescens.
abstract: The stereochemistry of the hydrogen transfer to NAD catalyzed by D-galactose dehydrogenase (E.C. 1.1.1.48) from P. fluorescens was investigated. The label at C-1 of D-[1--3H] galactose was enzymatically transferred to NAD and the resulting [4--3H]NADH was isolated and its stereochemistry at C-4 investigated. It was found that the label was exclusively located at the 4(S) position in NADH which calls for classification as a B-enzyme. This result was confirmed by an alternate approach in which [4--3H]NAD was reduced by D-galactose as catalyzed by D-galactose dehydrogenase. The sterochemistry at C-4 of the nicotinamide ring would then have to opposite to that in the first experiment. As expected, the label was now exclusively located in the 4(R) position, again confirming the B-calssification of the enzyme.
mesh_terms: D000429:Alcohol Oxidoreductases / Q000145:classification / Q000378:metabolism*; D005690:Galactose; D006859:Hydrogen / Q000378:metabolism; D009243:NAD / Q000378:metabolism*; D011551:Pseudomonas fluorescens / Q000201:enzymology*; D013237:Stereoisomerism
chemical_list: D009243:NAD; D006859:Hydrogen; D000429:Alcohol Oxidoreductases; D005690:Galactose