Department of Chemistry, University of Tromsø, Norway.
An elastase I-like enzyme was purified to homogeneity from the pyloric caeca of North Atlantic salmon (Salmo salar) and compared with porcine elastase I. The molecular weight and isoelectric point were estimated to be 27 kDa and over 9.3, respectively. The pH optimum was between 8.0 and 9.5, and the enzyme was unstable at pH values below 4. Kinetic properties examined using Suc-(Ala)3-p-nitroanilide showed that the catalytic efficiency of salmon elastase was about 2.5 times higher than that of porcine elastase. Furthermore, the salmon enzyme was less stable at lower pH values and temperatures than the porcine enzyme. The preference for amino acids at the primary binding site was found to be different from that of the porcine elastase. The salmon elastase binding pocket seems to prefer more branched aliphatic residues than the porcine elastase.