title: Properties of meso-alpha,epsilon-diaminopimelate D-dehydrogenase from Bacillus sphaericus.
abstract: meso-alpha,epsilon-Diaminopimelate D-dehydrogenase, which has been purified to homogeneity from the extract of Bacillus sphaericus IFO 3525, has a molecular weight of about 80,000 and consists of two subunits identical in molecular weight (approximately 40,000). The enzyme has a high substrate specificity. In addition to meso-alpha,epsilon-diaminopimelate, lanthionine is deaminated by the enzyme to a far lesser extent. NADP+ is the exclusive cofactor. The pH optima were at about 10.5 for the deamination of meso-alpha,epsilon-diaminopimelate and at 7.5 for its amination. L and D isomers of alpha,epsilon-diaminopimelate and meso-alpha,delta-diaminoadipate competitively inhibit the oxidation of meso-alpha,epsilon-diaminopimelate. Initial velocity and product inhibition studies show that the reductive amination proceeds through a sequential ordered ternary-binary mechanism. NADPH binds first to the enzyme followed by L-alpha-amino-epsilon-ketopimelate and ammonia, and the products are released in the order of meso-alpha,epsilon-diaminopimelate and NADP+. The Michaelis constants are as follows: meso-alpha,epsilon-diaminopimelate (2.5 mM), NADP+ (83 micro M), NADPH (0.2 mM), L-alpha-amino-epsilon-ketopimelate (0.24 mM), and ammonia (12.5 mM). The pro-S hydrogen at C-4 of the dihydronicotinamide ring of NADPH is transferred to the substrate; the enzyme is B-stereospecific. Fluorometric study on binding of NADPH to the enzyme revealed that the enzyme contains two coenzyme binding sites per molecule.
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D001407:Bacillus / Q000201:enzymology*; D001667:Binding, Competitive; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D009249:NADP / Q000494:pharmacology; D013379:Substrate Specificity
chemical_list: D046911:Macromolecular Substances; D009249:NADP; D000594:Amino Acid Oxidoreductases; C020032:diaminopimelate dehydrogenase