Extraction and enzymatic degradation of antimicrobial peptides, alpha andbeta-thionins, from barley and wheat [Japanese]

摘要

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