Abstract:

The mechanism of postmortem tenderization of muscle has been controversial for years. It is generally accepted
that the improvement of meat tenderness mainly results from five endogenous proteolytic enzymes, including lysosomal
cathepsin, proteasome, calpain, calpastatin and caspase. Calpains were widely considered to be a major contributor; however
the latest studies reveal the role of caspases in muscle tenderness. The molecular weights, distribution, substrates, action
sites, activation conditions, optimum pH and inhibitors of five enzymes involved in meat tenderization are briefly reviewed
in this paper. The possible activation pathways and transformation ways of the enzymes are also discussed with the aim of
providing a guideline for the application of these proteolytic enzymes to improve meat tenderness.

Key words: postmortem tenderization, protease, physiological and biochemical properties