Takaoka M, Miyata Y, Takenobu Y, Ikegawa R, Matsumura Y, Morimoto S
Department of Pharmacology, Osaka University of Pharmaceutical Sciences, Japan.
Biochem J. 1990 Sep 1;270(2):541-4. doi: 10.1042/bj2700541.
Pig endothelin-1 [ET-1-(1-21)] seems to be produced via proteolytic processing between Trp-21 and Val-22 of an intermediate form consisting of 39 amino acid residues, termed big ET-1-(1-39), by a chymotrypsin-like proteinase. We examined the chymotryptic-cleavage sites of big ET-1-(1-39) by reverse-phase h.p.l.c. and sequence analysis, and found that chymotrypsin cleaved initially the Tyr-31-Gly-32 bond of big ET-1-(1-39), followed by cleavage between Trp-21 and Val-22. Furthermore, chymotrypsin hydrolysed the generated ET-1-(1-21), producing a single major product that had the same amino acid sequence as ET-1-(1-21) with a cleavage between Tyr-13 and Phe-14. The disulphide bridge between Cys-1 and Cys-15 remained intact. These results indicate that the conversion of big ET-1-(1-39) into ET-1-(1-21) catalysed by chymotrypsin requires hydrolysis of the Tyr-31-Gly-32 bond before that of the Trp-21-Val-22 bond, an event followed by cleavage between Tyr-13 and Phe-14 within the loop of ET-1-(1-21). Thus a chymotrypsin-like proteinase might be involved not only in the production but also in the degradation of ET-1-(1-21) in vivo.
猪内皮素-1 [ET-1-(1-21)] 似乎是由一种类胰凝乳蛋白酶样蛋白酶在一种由39个氨基酸残基组成的中间形式（称为大ET-1-(1-39)）的色氨酸-21和缬氨酸-22之间进行蛋白水解加工而产生的。我们通过反相高效液相色谱法和序列分析研究了大ET-1-(1-39)的胰凝乳蛋白酶切割位点，发现胰凝乳蛋白酶最初切割大ET-1-(1-39)的酪氨酸-31-甘氨酸-32键，随后在色氨酸-21和缬氨酸-22之间进行切割。此外，胰凝乳蛋白酶水解生成的ET-1-(1-21)，产生一种单一的主要产物，其氨基酸序列与ET-1-(1-21)相同，在酪氨酸-13和苯丙氨酸-14之间有一个切割位点。半胱氨酸-1和半胱氨酸-15之间的二硫键保持完整。这些结果表明，胰凝乳蛋白酶催化大ET-1-(1-39)转化为ET-1-(1-21)需要在色氨酸-21-缬氨酸-22键水解之前先水解酪氨酸-31-甘氨酸-32键，这一事件之后是在ET-1-(1-21)环内的酪氨酸-13和苯丙氨酸-14之间进行切割。因此，一种类胰凝乳蛋白酶样蛋白酶可能不仅参与体内ET-1-(1-21)的产生，还参与其降解。
