Angiotensin-converting enzyme associated with Torpedo californica electric organ membranes
✍ Scribed by M. Altstein; Y. Dudai; Dr. Z. Vogel
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- English
- Weight
- 638 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0360-4012
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✦ Synopsis
Torpedo electric organ contains high concentrations of angiotensin converting enzyme (ACE) like activity, cleaving [Leu5]enkephalin at the Gl$-Phe4 peptide bond. Most of the activity cosediments with the cell membranes. The enzymatic preparation from membranes is inhibited by low concentrations of the ACE inhibitors, SQ 14225 and SQ 20881 (IC50 of 0.6 and 15 nM, respectively), and is weakly inhibited by the neutral endopeptidase inhibitors, phosphoramidon and thiorphan (IC50 of 30 pM and ca. 70 nM, respectively). The enzyme degrades hippuryl-His-Leu and is activated by NaCl. Hippuryl-His-Leu and [Leu5]enkephalin are degraded with Km of 93 and 41 pM, and V,,, of 21 and 10 nmol/mg proteidmin, respectively.
The specific activity of the ACE-like activity in homogenates of Torpedo electric organ is relatively high (6.3 nmol hippuryl-His-Leu/mg proteinlmin); this value is similar to that obtained for rat lung and rat striatum.