Effect of selected compounds on the activity of glutamate dehydrogenase from triticale roots

The influence of selected factors on the activity of highly purified GDH in triticale roots was investigated in vitro. In the presence of 2-ME, NADH-GDH activity increased by 400 %, while NADPH-GDH activity rose by 500 %. No effect of reducing factors on NAD(P)⁺-GDH reaction was detected. The sulphydryl groups inhibitors, such as p-chloromercuribenzoate (p-CMB) and iodoacetamide, proved the strongest inhibitors of the aminative reaction. Metal-binding compounds: ethylenediaminetetraacetic acid disodium salt (EDTA) and Zinkov also considerably inhibited NAD(P)H-GDH activity. Diisopropylfluorophosphate (DFP) and pepstatin A, the inhibitors specific for -OH serine and COO⁻ aspartic acid groups respectively, caused a non-significant NAD(P)H-GDH activity decrease. Cd²⁺, Co²⁺, Hg²⁺, Mg²⁺, Pb²⁺ and Zn²⁺ ions strongly inhibited the amination reaction, whereas their inhibiting effect upon NAD⁺-GDH activity was negligible. Among the applied ions, only Ca²⁺ activated NADH-GDH.