COENZYME ANALOG INHIBITORS OF APOGLUTAMATE DECARBOXYLASE

Bacterial glutamate decarboxylase apoenzyme reacts slowly with 5-nitrosalicylaldehyde to form a Schiff base which is devoid of catalytic activity. The inhibition constant is 1.1 mM at 0°, pH 5.4. Binding of this aldehyde prevents the recovery of catalytic activity on addition of pyridoxal phosphate. The binding reaction is accelerated by inorganic phosphate and inhibited by acetate. The apoenzyme is also inhibited by 3-nitrosalicylaldehyde (inhibition constant 2 mM), 3,5-dinitrosalicylaldehyde (6 mM), and 2-hydroxy-5-nitroacetophenone (8 mM). Results of kinetic and equilibrium binding studies on 5-nitrosalicylaldehyde indicate that this is not a simple one-step binding process, but that more than one kinetically significant step is involved. © 1969, American Chemical Society. All rights reserved.