Inhibition of Proteolytic Enzymes from Pseudomonas fluorescens ATCC 948 and Angiotensin I-Converting Enzyme by Peptides from Zein, Hordein, and Gluten Hydrolysates

Peptides inhibitory to partially purified endopeptidase and crude proteinase from Pseudomonas fluorescens ATCC 948 were isolated from tryptic hydrolysates of zein and hordein by reversed-phase fast protein liquid chromatography and identified by sequencing. The sequences are Ser-Ala-Tyr-Pro-Gly-Gln-Ile-Thr-Ser-Asn and Gln-Val-Ser-Leu-Asn-Ser-Gly-Tyr-Tyr for peptides from zein and hordein, respectively. Inhibitions of >85% and from >50 to >85% were determined on endopeptidase and proteinase by peptides from zein and hordein. K_i values ranged from 4 to 32 μM. The same peptides also showed inhibition of the angiotensin I-converting enzyme. The concentrations of peptides providing 50% inhibition of angiotensin I-converting enzyme were 7 and 23 μM for the decapeptide and nonapeptide, respectively. Other fractions containing peptides with less inhibitory activity were detected in the zein as well as in the gluten tryptic digests.