Examination of the role of thiolimidate formation in the cleavage of acetoacetyl-CoA catalyzed by thiolase I from porcine heart.
Examination of the role of thiolimidate formation in the cleavage of acetoacetyl-CoA catalyzed by thiolase I from porcine heart.
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DOI：
10.1016/0003-9861(89)90242-7
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发表时间：
1989-08
影响因子：
3.9
通讯作者：
E. Izbicka;H. Gilbert
中科院分区：
文献类型：
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作者：
E. Izbicka;H. Gilbert
通过化学修饰和同位素交换实验，研究了在猪心脏3-酮酰基辅酶A硫解酶(硫解酶I)催化的碳-碳键形成反应中，硫酰亚胺的形成对乙酰辅酶A的α-质子动力学酸性增加的潜在贡献。通过还原甲基化、磷酸吡哆醛、邻苯二甲醛(邻位赖氨酸和半胱氨酸专有)对赖氨酸残基进行化学修饰后，硫解酶仅部分失活。硫解酶催化乙酰辅酶A与Coash在18OH中生成乙酰辅酶A，产物中不伴随有18O的存在。这些实验有效地排除了硫代亚胺形成参与硫解酶反应的可能性。必须采用其他机制来促进硫解酶I对乙酰辅酶A的α-质子的提取。
The potential contribution of thiolimidate formation to the increased kinetic acidity of the α-proton of acetyl-CoA in the carbon-carbon bond forming reaction catalyzed by 3-ketoacyl-CoA thiolase (thiolase I) from porcine heart was assessed by chemical modification and isotope exchange experiments. Thiolase is only partially inactivated after the chemical modification of lysine residues by reductive methylation, pyridoxal phosphate, oro-phthaldehyde (specific for vicinal lysine and cysteine). The thiolase-catalyzed formation of acetyl-CoA from acetoacetyl-CoA and CoASH in18OH2is not accompanied by the appearance of18O in the acetyl-CoA product. These experiments effectively rule out participation of thiolimidate formation in the thiolase reaction. Other mechanisms must be employed to facilitate the abstraction of the α-proton of acetyl-CoA by thiolase I.