Mechanism-based inactivation of γ-aminobutyric acid aminotransferase by 3-amino-4-fluorobutanoic acid
作者:Richard B. Silverman、Cheryl L. Chamberlain Roscher
DOI:10.1016/0968-0896(96)00145-9
日期:1996.9
and no transamination, as determined by the lack of conversion of [1-14C] alpha-ketoglutarate into [1-14C] glutamate during inactivation, was observed. In the case of 1, the conclusion was that inactivation was completely the result of modification of the coenzyme and that there was no metabolic turnover; every enzyme molecule catalysed the conversion of one molecule of inactivator to the activated species
研究了3-氨基-4-氟丁酸(2)对吡咯醛5'-磷酸(PLP)依赖性酶γ-氨基丁酸(GABA)氨基转移酶的失活机理。与同系物一样,由2个当量的放射性标记的灭活剂(4-氨基-5-氟戊酸)共价连接到酶上,并且没有转氨作用,这是由[1-14C]α缺乏转化所决定的在灭活过程中观察到β-酮戊二酸转化为[1-14C]谷氨酸。在1的情况下,结论是灭活完全是辅酶修饰的结果,并且没有代谢转换。每个酶分子都催化一个灭活剂分子转化为被激活的物质,后者通过烯胺机制使酶失活。但是使用2,6.7 +/- 0。在灭活过程中释放了7当量的氟离子,并且需要7.6 +/- 0.7灭活剂分子才能灭活每种酶二聚体。由于没有发生转氨作用,因此酶的PLP形式还必须导致灭活以外的另一种代谢事件。用[1,2-14C] -2灭活GABA氨基转移酶产生了[14C]乙酰乙酸(约5.5当量)作为代谢产物。用[1,2-14C] -2灭活并凝胶过滤后,与酶共价结合的1