Gastric proteases of the Greenland cod Gadus ogac . I. Isolation and kinetic properties

• Published in: Biochemistry and Cell Biology
• Main Authors: Squires, E. James, Haard, N. F., Feltham, L. A. W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1986
• Subjects: Cell Biology; Molecular Biology; Biochemistry; Gadus ogac; Greenland; Greenland cod
• Online Access: http://dx.doi.org/10.1139/o86-030; http://www.nrcresearchpress.com/doi/pdf/10.1139/o86-030

The zymogens of three gastric proteases of the Greenland cod (Gadus ogac) were isolated by exclusion chromatography and chromatofocusing. The cod zymogens were activated more rapidly at lower temperatures than porcine pepsinogen and, after activation, were further purified by exclusion chromatography. The cod proteases had more alkaline pH optima and were active over a wider range of pH than porcine pepsin. The specific activity of porcine pepsin on protein substrates was greater than that of the individual cod proteases. However, the cod proteases had cumulative activity on protein substrates that was greater than the sum of their individual activities. Cod protease I was active on pepsin-specific substrates, and cod proteases 2 and 3 were active as gastricsin-specific substrates. All three cod proteases had greater milk-clotting activity and hydrolysed hemoglobin to a greater extent than porcine pepsin. The V max and K m,app of the cod proteases were dependent upon the substrate, and V max /K m,app values of the cod proteases were generally lower than porcine pepsin. It is suggested that the cod proteases together exhibit broad substrate specificity and maintain activity over a wide range of conditions to enhance protein digestion in the cod stomach.