Angiotensin I-converting enzyme inhibitors derived from an enzymatic hydrolysate of casein. Part V. Angiotensin I-converting enzyme inhibitory activity of the C-terminal hexapeptide of .ALPHA.s1-casein.

Abstract

Thr-Thr-Met-Pro-Leu-Trp, the C-terminal hexapeptide of αs1-casein, inhibited the angiotensin I-converting enzyme (I50 = 16 μM). Z-Pro-Leu-Trp also inhibited the enzyme (I50 = 18μM). 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=2.9μM). The antihypertensive activity of this hexapeptide was also investigated. This peptide, when intravenously administered to anesthetized rats at 31.8mg/kg, tended to antagonize the rats' pressor response to angiotensin I.