PROPERTIES OF ELASTASE FROM ATLANTIC COD, A COLD-ADAPTED PROTEINASE

An intestinal elastase was purified from Atlantic cod (Gadus morhua) o f apparent molecular mass 24.8 kDa as determined by SDS-PAGE and with isoelectric Point above pI 9.3. Heat stability and stability towards a cidic pH was reduced in the cod enzyme as compared with porcine intest inal 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 po rcine 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 h igher turnover rate (k(cat)) as compared with the porcine enzyme, and slightly higher K(m) values. Thus, the catalytic efficiency (k(cat)/K( m)) of Atlantic cod elastase was about 2-times higher than observed wi th porcine elastase, which indicates an adaptive response towards the low temperature environmental in which the cod lives. Substrate specif icity was studied by digestion of oxidized B-chain of insulin and by u sing synthetic substrates. Digestion was most rapid at the carbonyl si de of alanine residues, but also occurred at valine and leucine residu es.