Orning L, Krivi G, Bild G, Gierse J, Aykent S, Fitzpatrick F A
Department of Pharmacology, University of Colorado Health Science Center, Denver 80262.
J Biol Chem. 1991 Sep 5;266(25):16507-11.
Captopril ((2S)-1-(3-mercapto-2-methyl-propionyl)-L-proline) inhibited the bifunctional, Zn(2+)-containing enzyme leukotriene A4 hydrolase/aminopeptidase reversibly and competitively with Ki = 6.0 microM for leukotriene B4 formation and Ki = 60 nM for L-lysine-p-nitroanilide hydrolysis at pH 8. Inhibition was independent of pH between pH 7 and 8, the optimum range for each catalytic activity. Half-maximal inhibition of leukotriene B4 formation by intact erythrocytes and neutrophils required 50 and 88 microM captopril, respectively. In neutrophils and platelets neither 5(S)-hydroxyeicosatetraenoic acid, 12(S)-hydroxyeicosatetraenoic acid, nor leukotriene C4 formation were reduced, indicating selective inhibition of leukotriene A4 hydrolase/aminopeptidase, not 5-lipoxygenase, 12-lipoxygenase, or leukotriene C4 synthase. In whole blood, captopril inhibited leukotriene B4 formation with an accompanying redistribution of substrate toward formation of cysteinyl leukotrienes. The decrease in leukotriene B4 was more substantial than the corresponding increase in cysteinyl leukotrienes suggesting that nonenzymatic hydration predominates over transcellular metabolism of leukotriene A4 by platelets during selective inhibition of leukotriene A4 hydrolase. Enalapril dicarboxylic acid and Glu-Trp-Pro-Arg-ProGln-Ile-Pro-Pro which inhibit angiotensin-converting enzyme: angiotensin I, bradykinin, and N-[3-(2-furyl)acryloyl]Phe-Gly-Gly which are substrates; and chloride ions which activate angiotensin-converting enzyme did not modulate leukotriene A4 hydrolase/aminopeptidase activity. The results indicate that: (i) the sulfhydryl group of captopril is an important determinant for inhibition of leukotriene A4 hydrolase/aminopeptidase, probably by binding to an active site Zn2+; (ii) aminopeptidase and leukotriene A4 hydrolase display differential susceptibility to inhibition; (iii) there is minimal functional similarity between angiotensin-converting enzyme (peptidyl dipeptidase) and leukotriene A4 hydrolase/aminopeptidase; (iv) captopril may be a useful prototype to identify more potent and selective leukotriene A4 hydrolase inhibitors.
卡托普利（(2S)-1-(3-巯基-2-甲基丙酰基)-L-脯氨酸）可逆且竞争性地抑制双功能含锌（Zn²⁺）酶白三烯A4水解酶/氨肽酶，在pH 8时，对白三烯B4形成的抑制常数Ki = 6.0微摩尔，对L-赖氨酸-对硝基苯胺水解的抑制常数Ki = 60纳摩尔。在pH 7至8（每种催化活性的最佳范围）之间，抑制作用与pH无关。完整红细胞和中性粒细胞对白三烯B4形成的半数最大抑制分别需要50和88微摩尔卡托普利。在中性粒细胞和血小板中，5(S)-羟基二十碳四烯酸、12(S)-羟基二十碳四烯酸以及白三烯C4的形成均未减少，表明对白三烯A4水解酶/氨肽酶有选择性抑制，而非对5-脂氧合酶、12-脂氧合酶或白三烯C4合酶的抑制。在全血中，卡托普利抑制白三烯B4的形成，并伴随底物向半胱氨酰白三烯形成的重新分布。白三烯B4的减少比半胱氨酰白三烯相应的增加更为显著，这表明在选择性抑制白三烯A4水解酶期间，白三烯A4的非酶水合作用比血小板的跨细胞代谢更为显著。抑制血管紧张素转换酶的依那普利二羧酸和Glu-Trp-Pro-Arg-ProGln-Ile-Pro-Pro；血管紧张素转换酶的底物血管紧张素I、缓激肽和N-[3-(2-呋喃基)丙烯酰基]苯丙氨酰-甘氨酰-甘氨酸；以及激活血管紧张素转换酶的氯离子均未调节白三烯A4水解酶/氨肽酶的活性。结果表明：（i）卡托普利的巯基可能通过与活性位点的Zn²⁺结合，是抑制白三烯A4水解酶/氨肽酶的重要决定因素；（ii）氨肽酶和白三烯A4水解酶对抑制的敏感性不同；（iii）血管紧张素转换酶（肽基二肽酶）与白三烯A4水解酶/氨肽酶之间的功能相似性极小；（iv）卡托普利可能是鉴定更有效和选择性白三烯A4水解酶抑制剂的有用原型。
