Purification and Characterization of Glutamate Dehydrogenase from Ovine Brain

Glutamate dehydrogenase (GDH) is an enzyme that catalyzes both the reversible conveision of ammonium nitrogen into organic nitrogen (glutamate production) and the oxidative deamination of glutamate .resulting in a-oxoglutarate. GDH was purified from ovine brain to homogeneity on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme has a molecular mass of about 300 kOa and consists of six subunits with identical molecular masses of 53 kDa. Ovine brain GDH utilized both coenzymes NADH and NADPH. The Km values for glutamate at a fixed concentration of NAD* and NADP+ were 4.4 and 7.1 mM respectively, and for a-oxoglutarate at fixed concentrations of NADH and NADPH were 3.2 and 1.1 mM respectively. The enzyme was purified 564-fold with a specific activity of 124 U/mg.