Comparative studies of the proteolytic activity of tissue extracts from cod (Gadus morhua) and herring (clupea harengus)

Abstract 1. 1. A survey has been made of the proteolytic activities in distinct tissue fractions of herring ( Clupea harengus ) and cod ( Gadus morhua ). 2. 2. The proteolytic activity of the intestinal and liver fractions dominated in both fishes. 3. 3. The maximum proteolytic activity appeared in all tissues at pH 3–4.5 at a temperature of 45–60°C. 4. 4. Heat-stable alkaline proteases were detected in herring muscle. Optimal activity was found at pH 8 and a temperature of 62°C. The activity dropped off remarkably at temperatures below 58°C and above 65°C. 5. 5. Remarkably high acidic proteolytic activity was found in cod liver.