Drummer O H, Miach P, Jarrott B
Biochem Pharmacol. 1983 May 15;32(10):1557-62. doi: 10.1016/0006-2952(83)90327-1.
The presence of a methyltransferase enzyme in human red blood cells (RBCs) capable of S-methylation of captopril is described. The apparent Michaelis-Menten (Km) constant for captopril was 0.5 mM and the maximum velocity (Vmax) was 0.391 pmoles S-methylcaptopril (mg protein)-1 min-1. There is some evidence presented to show that S-methylcaptopril inhibited its own formation with a ki value of 5.81 mM. Captopril thiol methyltransferase activity was also examined in rat tissues and was found to be present in all tissue studied. Subcellular localisation studies in rat liver suggest that the enzyme was microsomal in origin. The order of activity was liver greater than heart greater than spleen greater than lung greater than kidney much greater than RBC (rat). This tissue distribution was quite different from previous studies using other thiol substrates and is consistent with more than one form of thiol methyltransferase enzyme in tissues.
本文描述了人类红细胞（RBC）中存在一种能够将卡托普利进行S-甲基化的甲基转移酶。卡托普利的表观米氏（Km）常数为0.5 mM，最大反应速度（Vmax）为0.391皮摩尔S-甲基卡托普利/（毫克蛋白·分钟）。有证据表明，S-甲基卡托普利以5.81 mM的抑制常数（ki）抑制其自身的形成。还对大鼠组织中的卡托普利硫醇甲基转移酶活性进行了检测，发现所有研究的组织中均存在该酶。对大鼠肝脏的亚细胞定位研究表明，该酶起源于微粒体。活性顺序为肝脏＞心脏＞脾脏＞肺＞肾脏＞红细胞（大鼠）。这种组织分布与先前使用其他硫醇底物的研究有很大不同，这与组织中存在不止一种形式的硫醇甲基转移酶是一致的。
