Poulsen K, Jacobsen J
J Hypertens. 1986 Feb;4(1):65-9. doi: 10.1097/00004872-198602000-00011.
The cleavage of the angiotensinogen molecule by renin is slow. The rate constant for cleavage of the enzyme-substrate complex, Kcat (turnover number) is lower than usual for enzymes (0.6/s for the homologous human renin reactions and 0.15/s for the homologous mouse renin reaction). Thus each round of catalysis occurs in 1.7 s in the human and 6.7 s in the mouse reaction. The Kcat/Km values (10(4)-10(6) l/mol per s; Km, Michaelis constant) are high and in the range for protein inhibitors. The association constants (Ka) are (10(6)-10(7) l/mol) close to that of inhibitors. The slow rate seems to be favourable since homologous reactions are slower than heterologous. Angiotensinogen is structurally related to alpha1-antitrypsin. We conclude that kinetic as well as structural data indicate that angiotensinogen might be considered a protease inhibitor for renin.
肾素对血管紧张素原分子的切割作用较为缓慢。酶 - 底物复合物切割的速率常数Kcat（转换数）低于一般酶的水平（同源人类肾素反应为0.6/秒，同源小鼠肾素反应为0.15/秒）。因此，在人类反应中每一轮催化发生在1.7秒，在小鼠反应中为6.7秒。Kcat/Km值（10⁴ - 10⁶升/摩尔·秒；Km为米氏常数）较高，处于蛋白质抑制剂的范围内。缔合常数（Ka）为（10⁶ - 10⁷升/摩尔），与抑制剂的相近。这种缓慢的速率似乎是有利的，因为同源反应比异源反应更慢。血管紧张素原在结构上与α1 - 抗胰蛋白酶相关。我们得出结论，动力学以及结构数据表明血管紧张素原可能被视为肾素的一种蛋白酶抑制剂。
