COVALENT BINDING OF ACETALDEHYDE SELECTIVELY INHIBITS THE CATALYTIC ACTIVITY OF LYSINE-DEPENDENT ENZYMES
COVALENT BINDING OF ACETALDEHYDE SELECTIVELY INHIBITS THE CATALYTIC ACTIVITY OF LYSINE-DEPENDENT ENZYMES
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DOI：
10.1002/hep.1840060218
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发表时间：
1986-03-01
期刊：
影响因子：
13.5
通讯作者：
TUMA, DJ
中科院分区：
文献类型：
--
作者：
MAUCH, TJ;DONOHUE, TM;TUMA, DJ
肝脏乙醇代谢产生活性中间体乙醛，乙醛与蛋白质结合。测定了乙醛与纯化酶的结合，以确定这种结合是否改变了它们的催化功能。[14C]乙醛与乙醇脱氢酶、葡萄糖-6-磷酸脱氢酶、乳酸脱氢酶和核糖核酸酶A分别在37度下孵育。C （pH 7.4）。在一些反应中，氰化硼氢化钠被用于稳定席夫碱，席夫碱是乙醛和酶的氨基之间反应形成的。除去每个反应混合物的一部分，以测定稳定加合物和总加合物（稳定加硼氢化物可还原）。乙醇脱氢酶和乳酸脱氢酶不受加合物形成的抑制。葡萄糖-6-磷酸脱氢酶和RNase的活性依赖于其催化位点上的赖氨酸残基，它们的活性受到剂量和时间依赖性的抑制。抑制程度与总加合物的形成直接相关。磷酸盐，已知抑制与RNase活性位点赖氨酸的结合，阻止了由加合物形成引起的催化活性抑制。这些发现表明乙醛与赖氨酸在催化位点的结合可以抑制酶的活性。
Hepatic ethanol metabolism generates the reactive intermediate, acetaldehyde, which binds to proteins. The binding of acetaldehyde to purified enzymes was determined in order to ascertain whether such binding altered their catalytic functions. [14C]Acetaldehyde was incubated with alcohol dehydrogenase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase and RNase A, each at 37.degree. C (pH 7.4). In some reactions, sodium cyanoborohydride was included for stabilization of Schiff bases, formed as a result of the reaction between acetaldehyde and the amino groups of the enzymes. Portions of each reaction mixture were removed for determination of stable and total (stable plus borohydride-reducible) adducts. Alcohol dehydrogenase and lactate dehydrogenase were not inhibited by adduct formation. Glucose-6-phosphate dehydrogenase and RNase, the activities of which depend on a lysine residue at their catalytic sites, were inhibited in a dose- and time-dependent manner. The degree of inhibition directly correlated with total adduct formation. Phosphate, known to inhibit binding to the active site lysine of RNase, prevented the inhibition of catalytic activity caused by adduct formation. These findings indicate that the binding of acetaldehyde to lysine at the catalytic site can inhibit enzyme activity.