Yu L, Yu C A
Biochim Biophys Acta. 1981 Sep 14;637(2):383-6. doi: 10.1016/0005-2728(81)90177-8.
(1) Purified succinate dehydrogenase contains about 49 mol of lysine residues per mol enzyme. Titration of succinate dehydrogenase with fluorescamine indicates that half the lysyl groups are located on the surface of the protein and the other half are buried inside. (2) The reconstitutive activity and the low Km ferricyanide reductase activity of succinate dehydrogenase decreased as the extent of alkylation of amino groups by fluorescamine increased. (3) The inhibitory effects of fluorescamine on both activities are parallel and are succinate concentration dependent. (4) Alkylation of the native succinate-Q reductase by fluorescamine does not affect the enzymatic activity or alter the enzyme kinetic parameters. This indicates that the inhibitory effect of fluorescamine on succinate dehydrogenase is due to the modification of a specific amino group(s) on succinate dehydrogenase which is essential in the interaction with QPs to form succinate-Q reductase. The participation of an ionic group in the formation of succinate-Q reductase supports the idea of the involvement of ionic interaction between succinate dehydrogenase and QPs.
(1) 纯化的琥珀酸脱氢酶每摩尔酶含有约49摩尔赖氨酸残基。用荧光胺滴定琥珀酸脱氢酶表明，一半的赖氨酰基团位于蛋白质表面，另一半则埋在内部。(2) 随着荧光胺对氨基的烷基化程度增加，琥珀酸脱氢酶的重组活性和低Km铁氰化物还原酶活性降低。(3) 荧光胺对这两种活性的抑制作用是平行的，且依赖于琥珀酸浓度。(4) 荧光胺对天然琥珀酸-Q还原酶的烷基化不影响酶活性或改变酶动力学参数。这表明荧光胺对琥珀酸脱氢酶的抑制作用是由于对琥珀酸脱氢酶上特定氨基的修饰，该氨基在与醌蛋白形成琥珀酸-Q还原酶的相互作用中至关重要。一个离子基团参与琥珀酸-Q还原酶的形成支持了琥珀酸脱氢酶与醌蛋白之间存在离子相互作用的观点。
