Effects of Protease Inhibitors on the Autolysis and Protease Activities of Antartic Krill

Abstract

In order to determine which proteases are responsible for the autolysis of krill, the effects of several protease inhibitors on the autolysis and protease activities of krill were investigated.Homogenates of whole bodies, and the cephalothorax and abdomen parts of frozen krill were equilibrated at 37°C at different pHs between 2 to 10 and allowed to stand for 16 hr, following which the increase in the TCA soluble fraction was monitored. 14C-Hemoglobin (14C-Hb) hydrolyzing activity was also measured using each homogenate as a crude enzyme preparation. The degree of autolysis and the 14C-Hb hydrolyzing activity were maximum at pH 5 ~ 8 for the parts studied. The hydrolytic activity was highest in the cephalothorax, followed by that in the whole body and then the abdomen.The effects of inhibitors on the 14C-Hb hydrolyzing activity were examined, and it was seen that soybean trypsin inhibitor (STI), diisopropyl fluorophosphate (DFP) and leupeptin significantly inhibited the activity at neutral pH, and pepstat...