Angiotensin I-converting enzyme inhibitory activities of synthetic peptides related to the tandem repeated sequence of a maize endosperm protein.

Abstract

Peptides that exist in the tandem repeated region formed by six units of Pro-Pro-Pro-Val-His-Leu in a maize endosperm protein γ-zein were chemically synthesized, and the angiotensin I-converting enzyme inhibitory activities of these peptides were investigated. Synthetic Val-His-Leu-Pro-Pro-Pro inhibited the enzyme (IC50=200 μM). Other synthetic fragment peptides, Val-His-Leu-Pro-Pro (IC50=18μM) and Leu-Pro-Pro (IC50=9.6μM) inhibited the enzyme more potently. Then the native hexapeptide Val-His-Leu-Pro-Pro-Pro was purified from a thermolysin hydrolysate of γ-zein. The antihypertensive activities of synthetic Val-His-Leu-Pro-Pro and Leu-Pro-Pro were also investigated. These peptides, when intravenously administered to anesthetized rats at 125mg/kg (Leu-Pro-Pro) or 160 mg/kg (Val-His-Leu-Pro-Pro), antagonized the rats' pressor response to angiotensin I.