Characterization of a pyridine nucleotide-nonspecific glutamate dehydrogenase from Bacteroides thetaiotaomicron.
An oxidized nicotinamide adenine dinucleotide phosphate/oxidized nicotinamide adenine dinucleotide (NADP+/NAD+) nonspecific L-glutamate dehydrogenase from Bacteroides thetaiotaomicron was purified 40-fold (NADP+ or NAD+ activity) over crude cell extract by heat treatment, (NH4)2SO2 fractionation, diethylaminoethyl-cellulose, Bio-Gel A 1.5m, and hydroxylapatite chromatography. Both NADP+- and NAD+-dependent activities coeluted from all chromatographic treatments. Moreover, a constant ratio of NADP+/NAD+ specific activities was demonstrated at each purification step. Both activities also comigrated in 6% nondenaturing polyacrylamide gels. Affinity chromatography of the 40-fold-purified enzyme using Procion RED HE-3B gave a preparation containing both NADP+- and NAD+-linked activities which showed a single protein band of 48,5000 molecular weight after sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis. The dual pyridine nucleotide nature of the enzyme was most readily apparent in the oxidative direction. Reductively, the enzyme was 30-fold more active with reduced NADP than with reduced NAD. Nonlinear concave 1/V versus 1/S plots were observed for reduced NADP and NH4Cl. Salts (0.1 M) stimulated the NADP+-linked reaction, inhibited the NAD+-linked reaction, and had little effect on the reduced NADP-dependent reaction. The stimulatory effect of salts (NADP+) was nonspecific, regardless of the anion or cation, whereas the degree of NAD+-linked inhibition decreased in the order to I- greater than Br- greater than Cl- greater than F-. Both NADP+ and NAD+ glutamate dehydrogenase activities were also detected in cell extracts from representative strains of other bacteroides deoxyribonucleic acid homology groups.
D000838:Anions; D001439:Bacteroides / Q000201:enzymology*; D002413:Cations, Divalent / Q000494:pharmacology; D005969:Glutamate Dehydrogenase / Q000302:isolation & purification / Q000378:metabolism*; D005971:Glutamates / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism; D007700:Kinetics; D009243:NAD / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013379:Substrate Specificity
D000838:Anions; D002413:Cations, Divalent; D005971:Glutamates; D007656:Ketoglutaric Acids; D009243:NAD; D012965:Sodium Chloride; D009249:NADP; D005969:Glutamate Dehydrogenase