摘要：In the present investigation, the occurrence of angiotensin I converting enzyme (EC 3. 4. 15. 1 ; ACE) was first demonstrated in the kidney of bullfrog (Rana catesbeiana). Namely, a large amount of hydrolyzing activity toward Nα-hippuryl-L-His-L-Leu-OH (HHL), a synthetic substrate of ACE, was detected in a 100000×g pellet fraction of the bullfrog kidney. The renal HHL hydrolyzing enzyme was solubilized from the 100000×g pellet with sodium deoxycholate. The solubilized bullfrog renal enzyme liberated H-His-Leu-OH from HHL. The enzyme activity was strongly activated by NaCl and slightly activated by cobalt sulfate in the presence of NaCl. These properties of the bullfrog renal enzyme agreed well with those of mammalian ACE previously reported. The bullfrog renal HHL hydrolyzing activity was completely inhibited by typical ACE inhibitors, ethylenediamine tetraacetic acid (10-3M), captopril (10-5M), SA-466 (10-5M) and MK-422 (10-6M). Furthermore, [Ile5]-angiotensin I converting activity was also detected in this enzyme fraction of bullfrog kidney and this converting activity was completely inhibited by MK-422 (10-6M). Thus, enzyme activities having characteristics of ACE were detected in the 100000×g pellet of bullfrog kidney. We also detected [Val5, Asn9]-angiotensin I (bullfrog angiotensin I) converting activity in the bullfrog renal extract. This converting activity was also completely inhibited by MK-422 (10-6M).
