Factors Contributing to Wort Nitrogen. II. Effects of Malting Time and Gibberellic Acid on Endopeptidase and Exopeptidase Activities

Abstract

Malts grown for 1–5 days were used for comparison of several proteolytic enzyme activities with published data on the release of N compounds during malting and mashing. The activities of carboxypeptidases on either carbobenzoxy-Phe-Phe or carbobenzoxy-Phe-Ala substrate increased rapidly, with no lag period during the first day of growth. The former activity was consistently stimulated throughout the 5-day growth period by gibberellic acid-treatment of the malts; the latter activity exhibited variable responses to such treatment from day to day during growth. Activities of aminopeptidases, with three aminoacyl-β-naphthylamides as substrates, were characteristically lower than those of the carboxypeptidases and increased only modestly with growing time. Only the activity of endopeptidase paralleled the soluble and free amino N contents of Larker and Piroline malts during growth. The early increases in carbobenzoxy peptidase activities were not reflected in the free amino N content of the malts. The data suggest that endopeptidase activity is the limiting factor for the solubilization of free amino N and of total soluble N in malt, and that carboxypeptidases are produced in excess of amounts required to hydrolyze the polypeptides that result from endopeptidase action.