Neutral and Alkaline Muscle Proteases of Marine Fish and Invertebrates a Review

Muscle proteases active at neutral and alkaline pH's include calcium-activated neutral proteases, heat-activated thiol proteases, serine proteases, and metallo-proteases. They participate to different extents in postmortem degradation of fish muscle myofibrillar and scaffold proteins. Their activity in fish, the presence of endogenous activators and inhibitors, pH, and temperature. Recent studies indicate that neutral and alkaline proteases have more impact on the postmortem deterioration in quality of fish muscles than the cathepsins active at acid pH. Significant quality losses are caused by enzymatic collagen degradation in raw tissues and by heat-activated enzymes in fish gels.