The "heterolytic hydroperoxide lyase" is an isomerase producing a short-lived fatty acid hemiacetal
The "heterolytic hydroperoxide lyase" is an isomerase producing a short-lived fatty acid hemiacetal
复制标题
DOI：
10.1016/j.bbalip.2003.12.003
复制
发表时间：
2004-02-27
影响因子：
4.8
通讯作者：
Hamberg, M
中科院分区：
文献类型：
--
作者：
Grechkin, AN;Hamberg, M
为了阐明氢过氧化物裂解酶 (HPL) 的反应机制，将来自番石榴 (Psidium guajava) 果实的酶与 13-HPOT 在 0 摄氏度下孵育 10-60 秒。产物被快速萃取并通过三甲基硅烷化衍生化。通过气相色谱-质谱 (GC-MS) 分析检测到两种捕获产物，即半缩醛 12-(1'-羟基-3'-己烯氧基)-9,11-十二碳二烯酸和烯醇 (9Z, 11E)-12 羟基-9,11-十二碳二烯酸的三甲基硅醚/酯衍生物。结构归属得到 (a) 氢化产物记录的质谱的支持； (b) 由[9,10,12,13,15,16] 13-HPOT或[O-18(2)]13-HPOT生物合成的产品； (c) 化学制备的参考化合物。动力学实验表明，半缩醛和烯醇都是不稳定且短暂出现的化合物（半衰期分别约为 20 秒和 2 分钟）。由[O-18(2)]13-HPOT生物合成的半缩醛和烯醇分别保留了2个和1个O-18原子，而[180]水中没有掺入180原子。数据表明：（1）13-HPOT在HPL存在下形成的真正酶产物是短寿命的半缩醛； (2)半缩醛自发解离成(3Z)-己烯醛和(9Z)-12-氧代-9-十二碳烯酸的不稳定烯醇形式； (3) 13-HPOT 酶促异构化为半缩醛，均裂发生。 (C) 2004 Elsevier B.V. 保留所有权利。
To elucidate the reaction mechanism of hydroperoxide lyase (HPL), the enzyme from guava (Psidium guajava) fruits, was incubated for 10-60 s at 0degreesC with 13-HPOT. The products were rapidly extracted and derivatized by trimethylsilylation. Two trapping products, namely the trimethylsilyl ether/ester derivatives of the hemiacetal 12-(1'-hydroxy-3'-hexenyloxy)-9,11-dodecadienoic acid and the enol (9Z, 11E)-12hydroxy-9,11-dodecadienoic acid, were detected by gas chromatography-mass spectrometry (GC-MS) analyses. The structural assignments were supported by mass spectra recorded for (a) hydrogenated products; (b) products biosynthesized from [9,10,12,13,15,16] 13-HPOT or [O-18(2)]13-HPOT; (c) chemically prepared reference compounds. Kinetic experiments showed that the hemiacetal and enol were both unstable and transiently appearing compounds (half-lives, ca. 20 s and 2 min, respectively). Hemiacetal and enol biosynthesized from [O-18(2)]13-HPOT retained two and one O-18 atoms, respectively, whereas no 180 was incorporated from [180]water. The data demonstrated that: (1) the true enzymatic product formed from 13-HPOT in the presence of HPL is a short-lived hemiacetal; (2) the hemiacetal spontaneously dissociates into (3Z)-hexenal and the unstable enol form of (9Z)-12-oxo-9-dodecenoic acid; (3) the enzymatic isomerization of 13-HPOT into the hemiacetal occurs homolytically. (C) 2004 Elsevier B.V. All rights reserved.