CATHEPSIN DEGRADATION OF PACIFIC WHITING SURIMI PROTEINS

Cathepsin B was the most active cysteine protease in Pacific whiting fish fillets; cathepsin L was predominant in surimi. Cathepsin L showed highest activity at 55 degrees C in both fish fillets and surimi, indicating its function in myosin degradation during conventional heating of fillets and surimi gels. Washing during surimi processing removed cathepsin B and B but not cathepsin L. Myosin heavy chain was the primary substrate during autolysis of surimi paste and actin and myosin light chain showed limited hydrolysis during 2 hr incubation. Purified Pacific whiting cathepsin L hydrolyzed myofibrils, myosin and native and heat-denatured collagen. The degradation pattern of myofibrils by the protease was the same as the autolytic pattern of surimi.