Extraction and Enzymatic Degradation of Antimicrobial Peptides, α and β-Thionins, from Barley and Wheat

Abstract

Antimicrobial peptides, α and β-thionins, were extracted from barley and wheat flour with 0.075-0.15N HCl. The degradation of α and β-thionins by digestive enzymes at 37°C was examined in vitro. No degradation of α-thionin was observed after the incubation of 10μg of barley α-thionin with 1μg of pepsin A for 16hr. Similar resuls were shown for wheat α-thionin and barley β-thionin. Denaturated wheat α-thionin by S-pyridylethyl modification of cystine residues was degraded by pepsin. Trypsin (0.5μg) and chymotrypsin (5μg) degraded 9.1μg and 7.2μg of wheat α-thionin for 1hr, and produced some partially hydrolyzed peptides. Similar results were obtained for barley α and β-thionins. The partially hydrolyzed peptides had no more antibacterial activity. The partially hydrolyzed peptides were almost completely degraded by leucine aminopeptidase and carboxypeptidase A.