Purification and Properties of NAD-dependent Glutamate Dehydrogenase from Phycomyces Spores

Summary: The NAD-dependent glutamate dehydrogenase from Phycomyces spores was purified more than 300-fold. Estimation of M r by gel filtration gave a value of 98000 whereas after SDS-PAGE one major band of M r 54000 was found, suggesting that the enzyme is a dimer. The enzyme was virtually dependent on the presence of AMP for activity and showed half-maximal activation at 9.5 and 43 μM-AMP in the direction of amination and deamination respectively. ADP was nearly as effective at 20-fold higher concentrations. Other nucleotide monophosphates were ineffective and nucleoside triphosphates were slightly inhibitory. Hyperbolic kinetics were found for all substrates yielding K m values of about 10 mM for ammonium, 1 mM for 2-oxoglutarate and 0.1 mM for NADH in the direction of amination, and 10 mM for glutamate and 0.7 mM for NAD in the direction of deamination.