Proteolysis in Cotyledon Cells of Phaseolus vulgaris L.: Changes in Multiple Hydrolase Activities Following Germination

Abstract

Changes in activity of several hydrolytic enzymes were measured in extracts prepared from the cotyledons following germination of bean seeds (Phaseolus vulgaris cv. Hawkesbury Wonder). Aminopeptidase AP2 (phenanthroline-sensitive leucyl β-naphthylamidase), N-carbobenzoxy-L- tyrosine-p-nitrophenol ester (N-CBZ-L-Tyr-pNP) hydrolase, N-benzoyl-L-tyrosineethyl ester (BTEE) hydrolase and acid phosphatase all increased in activity per cotyledon, reaching maximum values after 4, 6, 10 and 10 days respectively. By comparison, aminopeptidase AP1 (phenanthrolineinsensitive leucyl β-naphthylamidase) showed maximum activity after 2 days and declined immediately. α-N-benzoyl-D,L-arginine-p-nitroanilide hydrolase activity was maintained at a maximum value between days 2 and 10 before declining. Differences in maximum activity per cotyledon, initial presence or absence, and timing of both increase and decrease of N-CBZ-L-Tyr-pNP and BTEE hydrolase activities suggest that at least two enzymes contribute to these activities, and that neither activity indicates the presence of a chymotrypsin-like endopeptidase.