Kasuya F, Igarashi K, Fukui M, Nokihara K
Faculty of Pharmaceutical Sciences, Kobe-gakuin University, Japan.
Drug Metab Dispos. 1996 Aug;24(8):879-83.
Glycine conjugation is an important route of detoxification of many xenobiotic and endogenous carboxylic acids. A medium chain acyl-coenzyme A synthetase that catalyzes the first reaction of glycine conjugation was purified from bovine liver mitochondria by chromatographies on anion exchange, hydroxylapatite, affinity, and finally by gel filtration. The purified enzyme not only conjugates medium chain fatty acids, but also aromatic and arylacetic acids. The highest activity was shown with hexanoic acid. High activities were observed for benzoic acid derivatives with large alkyl and alkoxyl groups in the para- or meta-positions of the benzene ring. Ortho-substituted derivatives exhibited no activity. The enzyme was inhibited by iodoacetamide and salicylic acid, and activated by albumin. Salicylic acid was a competitive inhibitor of the enzyme, with an apparent Ki value of 37 microM. Enzyme activity increased 74% when the pH was raised from 7 to 10. Molecular weight of the purified medium chain acyl-coenzyme A synthetase was 65.5 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
甘氨酸结合作用是许多外源性和内源性羧酸解毒的重要途径。通过阴离子交换色谱、羟基磷灰石色谱、亲和色谱，最后通过凝胶过滤，从牛肝线粒体中纯化出一种催化甘氨酸结合作用第一步反应的中链酰基辅酶A合成酶。纯化后的酶不仅能结合中链脂肪酸，还能结合芳香酸和芳乙酸。己酸表现出最高活性。在苯环对位或间位带有大烷基和烷氧基的苯甲酸衍生物具有较高活性。邻位取代衍生物无活性。该酶受到碘乙酰胺和水杨酸的抑制，并被白蛋白激活。水杨酸是该酶的竞争性抑制剂，表观Ki值为37微摩尔。当pH从7升高到10时，酶活性增加74%。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳测定，纯化后的中链酰基辅酶A合成酶的分子量为65.5 kDa。
