Enzymatic Properties of Endopeptidase in Wheat Malt

Abstract

Endopeptidase is the main enzyme in wheat malt. Besides, long chain proteins are broken down by endopeptidase into small protein molecules, or peptides, which can influence the beer quality. In this paper, enzymatic properties of endopeptidase in wheat malt were studied based on a more accurate method for the endopeptidase activity measurement. The activity of endopeptidase was determined by measuring the content of oligopeptides and polypeptides in the reaction system. It was found that the optimum temperature of wheat malt endopeptidase was 50°C. It was shown that endopeptidase was sensitive to temperature and the low temperature is more suitable for endopeptidase. Further increase of temperature to values higher than 50°C resulted in the decrease of enzyme activity. At 65°C, the enzyme activity was decreased to 7.47u±0.42, then the enzyme can be deactivated at temperatures higher than 70°C. The enzyme had optimal activity at pH 4.0. When the pH value was above 4, the enzyme activity cannot remain stable after incubation. The enzyme was inhibited by Ca2 +, Pb2 +, Zn2+, Cu2 +, EDTA.