Nakae Y, Shono M
Histochem J. 1986 Apr;18(4):169-74. doi: 10.1007/BF01676117.
The kinetics of acetylation of mitochondrial succinate dehydrogenase [EC 1.3.99.1] in the two fibre types (A and C) of rat gastrocnemius with N-acetylimidazole was studied by a newly modified histochemical technique. Acetylimidazole partially inactivated the enzyme, but subsequent deacetylation with hydroxylamine restored the enzyme activity completely. Inactivation of the enzyme by acetylimidazole was prevented by malonate, which is a competitive inhibitor of the enzyme. The value of the inhibition constant (Ki = 34 microM) for malonate, obtained from the dependence of the pseudo-first order rate constant of acetylation of the enzyme with acetylimidazole on the malonate concentration, was in good agreement with the Ki value (33 microM) obtained by a different method, the dependence of the initial velocity of succinate oxidation by the dehydrogenase on the substrate concentration in the presence of malonate. These findings suggest that a tyrosyl residue is located in the malonate binding site (the active site) of succinate dehydrogenase in the gastrocnemius and plays a role in substrate binding, but is not a catalytic group.
采用一种新改良的组织化学技术，研究了用N - 乙酰咪唑对大鼠腓肠肌两种纤维类型（A和C）中线粒体琥珀酸脱氢酶[EC 1.3.99.1]进行乙酰化的动力学。乙酰咪唑使该酶部分失活，但随后用羟胺进行脱乙酰化可使酶活性完全恢复。丙二酸可防止乙酰咪唑对该酶的失活作用，丙二酸是该酶的竞争性抑制剂。根据酶与乙酰咪唑乙酰化的伪一级反应速率常数对丙二酸浓度的依赖性所得到的丙二酸抑制常数（Ki = 34 microM），与通过不同方法得到的Ki值（33 microM）相符，该不同方法是在丙二酸存在下，根据脱氢酶催化琥珀酸氧化的初始速度对底物浓度的依赖性来测定的。这些发现表明，在腓肠肌琥珀酸脱氢酶的丙二酸结合位点（活性位点）存在一个酪氨酰残基，它在底物结合中起作用，但不是催化基团。
