Potter D M, McDonald W J, Metcalfe J, Porter G
Am J Physiol. 1977 Nov;233(5):E434-8. doi: 10.1152/ajpendo.1977.233.5.E434.
It has previously been reported that in the dog the Michaelis constant (Km) of renal renin with respect to homologous plasma substrate is the same as that for the angiotensin-generating enzyme extractable from the myometrium during pregnancy. We have reexamined the kinetics with a different methodology. Enzyme preparations from dog kidneys, the uterus of a nonnephrectomized pregnant bitch, and the uterus of a nephrectomized pregnant bitch were used. The substrate, prepared by diluting plasma from a nephrectomized, hysterectomized pregnant bitch, had a maximum endogenous substrate concentration of 1,750 ng/ml angiotensin I equivalents. Lineweaver-Burk kinetic analysis was used to calculate the Michaelis constants at pH 6.2. The Km of the renal enzyme was 720 ng/ml, of the enzyme prepared from the nonnephrectomized uterus 1,570 ng/ml, and of the nephrectomized dog uterus 1,500 ng/ml. The uterine enzyme was not activated by transient acid treatment, in contrast to renins reported from other sources. The data support the concept of biochemical heterogeneity of the two enzymes in the dog.
此前有报道称，在犬类中，肾素相对于同源血浆底物的米氏常数（Km）与妊娠期间从子宫肌层中提取的血管紧张素生成酶的米氏常数相同。我们用不同的方法重新研究了动力学。使用了来自犬肾、未切除肾脏的妊娠母犬子宫以及切除肾脏的妊娠母犬子宫的酶制剂。底物是通过稀释切除肾脏、子宫切除的妊娠母犬的血浆制备的，其最大内源性底物浓度为1750 ng/ml血管紧张素I当量。采用Lineweaver-Burk动力学分析来计算pH 6.2时的米氏常数。肾酶的Km为720 ng/ml，从未切除肾脏的子宫制备的酶为1570 ng/ml，切除肾脏的犬子宫的酶为1500 ng/ml。与其他来源报道的肾素不同，子宫酶不会被短暂的酸处理激活。这些数据支持犬类中这两种酶存在生化异质性的概念。
