Oxidative decarboxylation activity of malic enzymes from the uropygial gland and the liver of duck was inhibited by sulfhydryl group directed reagents, DTNB, NEM, and PCMPS. The pseudo-first order plots for the inactivation by DTNB, NEM, and PCMPS wer...
Oxidative decarboxylation activity of malic enzymes from the uropygial gland and the liver of duck was inhibited by sulfhydryl group directed reagents, DTNB, NEM, and PCMPS. The pseudo-first order plots for the inactivation by DTNB, NEM, and PCMPS were linear. The number of total DTNB sensitive -SH groups in malic enzyme from the uropygial gland were 8, whereas those in the enzyme from the liver of duck were 12. However the number of -SH groups directly participated in the inactivation of oxidative decarboxylation activity of malic enzyme were only about three for both enzymes from the two different tissues. The inactivation of the enzyme was not protected by substrate or cofactor, suggesting that the reactive sulfhydryl groups of the enzyme may play an important role during the catalytic event but not binding the substrate and the cofactor on the active site.