Atlantic salmon (Salmo salar L.) skin contains a novel kininogen and another cysteine proteinase inhibitor

Abstract

We describe the purification and characterization of two novel cysteine proteinase inhibitors found in Atlantic salmon skin. One of these, salmon kininogen, has a molecular mass of 52 kDa as determined by matrix-assisted laser desorption/ionization time-of-flight MS, is multiply charged with pI values of 4.0, 4.2 and 4.6 and shows homology to kininogens including the bradykinin motif. The other, salarin, has a molecular weight of 43 kDa, a pI of 5.1 and shows weak homology to cysteine proteinases. Both proteins are N- and O-glycosylated and inhibit papain and ficin but not trypsin.