Beef liver glutamate dehydrogenase: A study of the oxidation of various alternative amino acid substrates retaining the correct spacing of the two carboxylate groups

Abstract

1. 1. Several glutamate analogues substituted at the β- or γ-carbon atoms have been tested as substrates for glutamate dehydrogenase. 2. 2. The two γ-methyl derivatives and DL-β-methylglutamate give the same pH optimum (8.7) as l-glutamate, but show inhibition by ADP and activation by GTP at pH 8, unlike glutamate and like the monocarboxylic substrate l-norvaline, which gives a pH optimum of 10. 3. 3. l-γ-methyleneglutamate, the poorest substrate tested (0.28% of rate with glutamate) gives a high pH optimum (10), like norvaline, but shows marked activation by both ADP (13-fold) and GTP (27-fold). 4. 4. Despite the correct dicarboxylate spacing, all the analogues were much poorer substrates than l-norvaline.