...
首页> 外文期刊>Biochemistry >Molecular oxygen dependent steps in fatty acid oxidation by cyclooxygenase-1.
【24h】

Molecular oxygen dependent steps in fatty acid oxidation by cyclooxygenase-1.

机译:分子氧依赖性步骤通过环加氧酶-1进行脂肪酸氧化。

获取原文
获取原文并翻译 | 示例
           

摘要

The mechanism by which cyclooxygenase-1 (COX-1), a heme- and tyrosyl radical-containing enzyme, catalyzes the regio- and stereospecific oxygenation of polyunsaturated fatty acids to prostaglandin or hydroperoxide products has not been understood. Steady-state kinetic studies conducted with the native substrate arachidonic acid and the slower substrate linoleic acid are described here. Second-order rate constants, kcat/KM for fatty acid and O2, are found to depend upon the concentration of the other cosubstrate. Competitive oxygen kinetic isotope effects (18O KIEs) kcat/KM(16,16O2)/kcat/KM(18,16O2) reveal that a peroxyl radical is formed in or before the first kinetically irreversible step. Together, the results indicate that the oxygenase reaction occurs by a sequential mechanism which most likely involves reversible abstraction of a hydrogen atom from the fatty acid prior to the trapping of the delocalized substrate radical by O2. The identity of the first kinetically irreversible step, subsequent to forming the peroxyl radical, is also discussed in the context of the magnitude of the oxygen kinetic isotope effects as well as the behavior of kcat/KM(O2) in response to changing solvent pH, pD, and viscosity.
机译:尚不清楚环氧化酶-1(COX-1)(一种含血红素和酪氨酰基基团的酶)催化多不饱和脂肪酸向前列腺素或氢过氧化物产物进行区域和立体定向氧化的机理。本文介绍了使用天然底物花生四烯酸和较慢的底物亚油酸进行的稳态动力学研究。发现脂肪酸和O2的二级速率常数kcat / KM取决于另一种共底物的浓度。竞争性氧动力学同位素效应(18O KIEs)kcat / KM(16,16O2)/ kcat / KM(18,16O2)表明,在第一个动力学不可逆步骤中或之前形成了过氧自由基。总之,结果表明加氧酶反应是通过顺序机制发生的,该顺序机制很可能涉及在通过O2捕获离域的底物自由基之前从脂肪酸可逆地提取氢原子。在氧动力学同位素效应的幅度以及响应溶剂pH值变化的kcat / KM(O2)行为的背景下,还讨论了形成过氧自由基之后的第一动力学不可逆步骤的身份, pD和粘度。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱:kefu@zhangqiaokeyan.com

京公网安备:11010802029741号 ICP备案号:京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有
  • 客服微信

  • 服务号