PROTEOLYTIC ACTIVITY OF CRUDE ENZYME EXTRACTS OF SQUID ILLEX-ARGENTINUS LIVER

The extract obtained from the acetone powder of frozen stored squid li ver had optimum proteolytic activity against hemoglobin at pH 2.6 to 4 .0. About 90% of the activity at pH 3.0 was inhibited by pepstatin and about 15% was inhibited by phenylmethanesulfonyl fluoride or iodoacet amide. The activity was increased by dithiothreitol and cysteine by ab out 55 and 40%, respectively. At pH 3 the enzyme extract had a tempera ture optimum of 45 to 50C; at 5C the activity was about 15% of that at 45 to 50C. At pH 7 the optimum activity was at about 45C. Heating of the extract without substrate at pH 3 and 7 caused a rapid decrease in proteolytic activity above 35 and 30C, respectively. A water extract of the liver was used to treat isolated bovine myofibrils at pH 5.5 an d 0C. After 20 h a fragment of slightly low m.w. than that of the myos in heavy chain was detected. After treatment at pH 7 and 0C, little de gradation of the myofibrillar proteins was evident. At 20C the myofibr ils were hydrolyzed to several products.