IDENTIFICATION OF TWO MATRIX METALLOPROTEINASES IN THE SKELETAL MUSCLE OF PACIFIC ROCKFISH (SEBASTES SP.)

Abstract

Two heat-stable metalloproteinases with collagenase activity have been identified in the skeletal muscle of Pacific rockfish (Sebastes sp.) and partially characterized. The 47 kDa and 95 kDa enzymes appear to be similar to mammalian matrix metalloproteinases (MMPs), with respect to molecular weight, pH-activity profile, substrate specificity, dependence on calcium for activity, and inhibition-activation profiles. The fish metalloproteinases readily hydrolyzed collagen and gelatin, but not β- or K-casein, in SDS-PAGE substrate zymograms. They also hydrolyzed collagen and gelatin in solution, but showed very low activity in solubilizing native fibrillar collagen. They did not hydrolyze solutions of β- or K-casein, azocasein, hide powder azure or synthetic substrates for trypsin, chymotrypsin or collagenase. To our knowledge, this is the first report where fish muscle proteinases have been identified as possible members of the family of MMPs. The rockfish muscle MMPs appear to be different from other currently identified fish muscle proteinases in regard to molecular weight, substrate specificity and activation-inhibition profiles. These two enzymes could be partly responsible for the degradation of collagen and other extracellular matrix proteins in fish muscle and for the texture softening of seafood products.