Purification and partial characterisation of a trypsin from the processing waste of the silver mojarra (Diapterus rhombeus)

Abstract

An alkaline peptidase was purified from the viscera of the silver mojarra (Diapterus rhombeus) in a three-step process: heat treatment, ammonium sulphate fractionation and molecular exclusion chromatography (Sephadex (R) G-75), with final specific activity 86-fold higher than the enzyme extract and yield of 22.1%. the purified enzyme had an estimated molecular mass of 26.5 kDa and NH2-terminal amino acid sequence IVGGYECTMHSEAHE. Higher enzyme activity was observed at pH 8.5 and between 50 and 55 degrees C. the enzyme was completely inactivated after 30 min at 55 degrees C and it was significantly more stable at alkaline pH. K-m, K-cat and K-cat center dot K-m(-1) values, using BApNA as substrate, were 0.266 mM, 0.93 s(-1) and 3.48 mM(-1) s(-1), respectively. Enzyme activity increased in the presence of the ions (1 mM) K+, Li+ and Ca2+, but was inhibited by Fe2+, Cd2+, Cu2+, Al3+, Hg2+, Zn2+ and Pb2+ as well as by the trypsin inhibitors TLCK and benzamidine. (C) 2011 Elsevier B.V. All rights reserved.