Kinetic-controlled hydrolysis of Leu-Val-Val-hemorphin-7 catalyzed by angiotensin-converting enzyme from rat brain |
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Authors: | Hayakari Makoto Satoh Kimihiko Izumi Hiroshi Kudoh Toshihiro Asano Junpei Yamazaki Takehiko Tsuchida Shigeki |
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Institution: | Second Department of Biochemistry, School of Medicine, Hirosaki University, 5 Zaifu-Cho, Hirosaki 036-8562, Japan. hayakari@cc.hirosaki-u.ac.jp |
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Abstract: | Leu-Val-Val-hemorphin-7 (LVV-H7, LVVYPWTQRY), an opioid peptide, was found to be hydrolyzed sequentially by rat brain angiotensin-converting enzyme (ACE) in three steps through dipeptidyl carboxypeptidase activity. The kinetic constants evaluated were in order of: k(1) (0.19 min(-1))>k(2) (0.0008 min(-1)) approximately k(3) (0.0006 min(-1)) in 10 mM NaCl at pH 7.5 giving rise to LVV-H5 almost quantitatively. The decapeptide was noted to be hydrolyzed 164- and 346-fold more efficiently than angiotensin I (Ang I) in k(cat) and kcat/Km values, respectively, at their optimal conditions. The kinetic-controlled preferential action of the brain enzyme on LVV-H7 is suggestive of its multiple roles in vivo. |
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