Bhatnagar A, Das B, Srivastava S K
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77550.
Biochim Biophys Acta. 1987 Nov 26;916(2):179-84. doi: 10.1016/0167-4838(87)90106-3.
Diethyl pyrocarbonate inactivated aldehyde reductase II (L-gulonate:NADP+ 6-oxidoreductase, EC 1.1.1.19) from human placenta. A concentration of 0.5-1.0 mM diethyl pyrocarbonate caused 40-65% loss of activity. The inactivation of the enzyme by diethyl pyrocarbonate was reversed by hydroxylamine and was accompanied by a large change in the absorbance of the protein at 242 nm, but not at 278 nm, indicating that only the histidine residues were modified. NADPH, but not glucuronate afforded significant protection to the enzyme from inactivation by diethyl pyrocarbonate. With 0.2-1.0 mM diethyl pyrocarbonate, 4-5 histidine residues were modified with a pseudo-first-order rate process. A double log plot of the fraction of the unmodified residues indicates that only one functional histidine residue is essential for the catalytic activity of aldehyde reductase II.
焦碳酸二乙酯可使来自人胎盘的醛还原酶II（L-古洛糖酸：NADP + 6-氧化还原酶，EC 1.1.1.19）失活。0.5-1.0 mM的焦碳酸二乙酯浓度会导致40-65%的活性丧失。焦碳酸二乙酯对该酶的失活作用可被羟胺逆转，并且伴随着蛋白质在242 nm处吸光度的大幅变化，但在278 nm处没有变化，这表明只有组氨酸残基被修饰。NADPH而非葡萄糖醛酸能为该酶提供显著保护，使其免受焦碳酸二乙酯的失活作用。在0.2-1.0 mM的焦碳酸二乙酯作用下，4-5个组氨酸残基以假一级反应过程被修饰。未修饰残基比例的双对数图表明，只有一个功能性组氨酸残基对醛还原酶II的催化活性至关重要。
