Influence of harvest season on the proteolytic activity of hepatopancreas and mantle tissues from jumbo squid (Dosidicus gigas)

Jumbo squid (Dosidicus gigas) size and protease activities were evaluated after harvest in April (A) and November (N). A were smaller (560 120 g vs 6040 1130 g) and hepatopancreas was a larger percent of body weight (8.3+/-2.5 vs 4.6+/-2.1). Mantle from A had lower water (73.9+/-1.1 vs 79.1+/-1.2) and higher protein (29.0+/-1.1 vs 23.1+/-0.8). Lipid and protein contents of N and A hepatopancreas tissues did not differ (P<0.05). Azocaseinolytic, trypsin-like, chymotrypsin-like, aminopeptidase, and carboxypeptidase activities were detected in mantle (ME) and hepatopancreas extracts (HPE). HPE and ME from N had higher activity than A for all substrates (P<0.05). With azocasein substrate, HPE activity from A had a pH optimum of 5 - 6 and a temperature optimum of 70C, whereas HPE from N had highest activity at pH 9 and 40-70C ME from A had maximum proteolytic activity at pH 6 and 60C, whereas that from N had maximum activity at pH 10 and 40C SDS-PAGE zymograms of HPE from A and N revealed different patterns of activity and I and 2 major protease zones, respectively.