Properties of elastase from Atlantic cod, a cold-adapted proteinase.

An intestinal elastase was purified from Atlantic cod (Gadus morhua) of apparent molecular mass 24.8 kDa as determined by SDS-PAGE and with isoelectric point above pI 9.3. Heat stability and stability towards acidic pH was reduced in the cod enzyme as compared with porcine intestinal elastase. N-terminal amino-acid sequence analysis of cod elastase showed considerable similarity with porcine elastase. The cod enzyme was less sensitive to phenylmethylsulfonyl fluoride inhibition than porcine elastase, but sensitivity towards other inhibitors was similar. Kinetic properties were examined using the substrate Suc-Ala-Ala-Ala-p-nitroanilide and the cod enzyme was found to have more than 2-times turnover rate (kcat) as compared with the porcine enzyme, and slightly higher Km values. Thus, the catalytic efficiency (kcat/Km) of Atlantic cod elastase was about 2-times higher than observed with porcine elastase, which indicates an adaptive response towards the low temperature environmental in which the cod lives. Substrate specificity was studied by digestion of oxidized B-chain of insulin and by using synthetic substrates. Digestion was most rapid at the carbonyl side of alanine residues, but also occurred at valine and leucine residues.