Hydrolytic Action of Salmon Cathepsins B and L to Muscle Structural Proteins in Respect of Muscle Softening

Abstract

Cathepsins B and L, lysosomal cysteine proteases, are suspected of causing the softening phenomenon of post-mortem muscle of salmon. The proteolytic action of these enzymes on structural proteins of fish muscle was investigated. Cathepsin L was capable of hydrolyzing the major muscle structural proteins, such as connectin, nebulin, myosin, collagen, a-actinin, and troponins T and I. Although cathepsin B hydrolyzed connectin, nebulin, and myosin, the hydroly-sis rate was very low and, furthermore, the hydrolytic action was limited to only these proteins. These findings indicate the direct participation of cathepsin L in drastic proteolytic degradation of the fine structure of muscle of the fish. © 1991, The Japanese Society of Fisheries Science. All rights reserved.