Angiotensin I-Converting Enzyme Inhibitory Activity of the C-Terminal Hexapeptide of α_s1-Casein

Abstract

Thr-Thr-Met-Pro-Leu-Trp, the C-terminal hexapeptide of αsl-casein, inhibited the angiotensin I-converting enzyme (I50 = 16 μM). Z-Pro-Leu-Trp also inhibited the enzyme (I50 = 18 μM). The Pro- Leu-Trp sequence may be important for the inhibitory activity of this hexapeptide. Z-Pro-Val-Trp, which contains Val in place of Leu, inhibited the enzyme more potently (I50 =2.9 μM). The antihypertensive activity of this hexapeptide was also investigated. This peptide, when intravenously administered to anesthetized rats at 31.8 mg/kg, tended to antagonize the rats’ pressor response to angiotensin I.