Partial Characterization of Protease Activity in Squid ( <i>Todaropsis eblanae</i> ) Mantle: Modification by High‐pressure Treatment

Abstract

ABSTRACT: Optimal conditions for proteolytic activity in both nonpressurized and pressurized (300 MPa, 7°C, 20 min) squid ( Todaropsis eblanae ) muscle occurred at acid pH levels (pH 3) over a broad range of temperatures. Pressure treatment did not modify optimal pH and temperatures but did increase proteolytic activity. The acid cysteine proteases, and to a lesser extent the acid serine proteases, were the enzymes mainly affected by the high‐pressure treatment. The sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) was indicative of increased protein hydrolysis by pressurization. Myosin heavy chain in both nonpressurized and pressurized squid was degraded at all the temperatures tested, but actin was susceptible only to proteolysis in the pressure‐treated muscle at 7°C and 40°C. This behavior was not observed at 55°C.