Vijayaraghavan J, Scicli A G, Carretero O A, Slaughter C, Moomaw C, Hersh L B
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas 75235.
J Biol Chem. 1990 Aug 25;265(24):14150-5.
Endothelins 1-3 are a family of 21-amino acid peptides whose structure consists of two rings formed by intra-chain disulfide bonds and a linear "COOH-terminal tail." These peptides were originally described on the basis of their potent vasoconstrictor activity. The hydrolytic inactivation of endothelin action has recently been implicated to be attributed, at least in part, to the enzyme neutral endopeptidase 24.11 (Scicli, A. G., Vijayaraghavan, J., Hersh, L., and Carretero, O. (1989) Hypertension 14, 353). The kinetic properties and mode of hydrolysis of the endothelins by this enzyme are reported in this study. The Km for endothelins 1 and 3 hydrolysis is approximately 2 microM while endothelin2 exhibits a 5-fold higher Km. Endothelins 1 and 2 exhibit similar Vmax values while endothelin3 is hydrolyzed considerably more slowly. The initial cleavage site in endothelin1 is at the Ser5-Leu6 bond located within one of the cyclic structures. Thermolysin, a bacterial neutral endopeptidase with a similar substrate specificity to neutral endopeptidase 24.11 initially cleaves endothelin1 between His16-Leu17 which lies within the COOH-terminal linear "tail" portion of the molecule. The cleavage of endothelins 2 and 3 by neutral endopeptidase 24.11 differs from that observed with endothelin1 in that cleavage of these endothelins occurs at Asp18-Ile19 within the linear COOH-terminal tail structure. These results demonstrate that the endothelins are good substrates for neutral endopeptidase 24.11 and suggest that their mode of cleavage is dependent upon both amino acid sequence as well as peptide conformation.
内皮素1 - 3是一族由21个氨基酸组成的肽，其结构由链内二硫键形成的两个环和一个线性的“羧基末端尾”组成。这些肽最初是根据其强大的血管收缩活性而被描述的。最近有研究表明，内皮素作用的水解失活至少部分归因于中性内肽酶24.11（Scicli, A. G., Vijayaraghavan, J., Hersh, L., and Carretero, O. (1989) Hypertension 14, 353）。本研究报道了该酶对内皮素的动力学性质和水解模式。内皮素1和3水解的Km约为2微摩尔，而内皮素2的Km值高5倍。内皮素1和2表现出相似的Vmax值，而内皮素3的水解则慢得多。内皮素1的初始切割位点在位于其中一个环状结构内的Ser5 - Leu6键处。嗜热菌蛋白酶是一种细菌中性内肽酶，其底物特异性与中性内肽酶24.11相似，最初在分子的羧基末端线性“尾”部分的His16 - Leu17之间切割内皮素1。中性内肽酶24.11对内皮素2和3的切割与内皮素1不同，因为这些内皮素的切割发生在线性羧基末端尾结构内的Asp18 - Ile19处。这些结果表明，内皮素是中性内肽酶24.11的良好底物，并表明它们的切割模式取决于氨基酸序列以及肽的构象。
