1985 年 105 巻 5 号 p. 491-498
Some properties of angiotensin I-converting enzyme existed in rat testis (RT-ACE) were compared with those of angiotensin I-converting enzyme in rat lungs (RP-ACE). In gel filtration through Sephadex G-200 column, distribution coefficient of RT-ACE (0.34) was higher than that of RP-ACE (0.27). Furthermore, RT-ACE migrated faster than RP-ACE on SDS-polyacrylamide gel electrophoresis. The molecular weights of RT-ACE and RP-ACE were estimated to be 104 and 150 kilodaltons, respectively, on the SDS-polyacrylamide gel electrophoresis. On the other hand, enzymo-chemical properties of both ACEs were very similar when they were assayed by using Nα-hippuryl-His-Leu-OH (HHL) as substrate. Namely, 1) HHL hydrolyzing activities of both ACEs were strongly activated by the addition of NaCl. And the effects of NaCl concentrations on the enzyme activities were similar between RT-ACE and RP-ACE. 2) The effects of various pH on the HHL hydrolyzing activities were also very similar between both ACEs under both conditions where NaCl was present or absent. 3) Km values for HHL hydrolysis of RT-ACE and RP-ACE were estimated to be the same (2.5 mM) at pH 8.3, in the presence of 0.8 M NaCl. 4) The HHL hydrolyzing activity of RT-ACE was inhibited by the addition of captopril or MK-422, specific inhibitors of angiotensin I-converting enzyme, to similar extent to RP-ACE. From these results, it was speculated that the portions of RT-ACE contributing to the appearance of enzyme activities would resemble those of RP-ACE although the molecule of RT-ACE is different from that of RP-ACE.