Post-mortem meat tenderization is driven by two major endogenous enzymatic systems: the cytosolic calpain system and the lysosomal cathepsin system. The Calpains (Calcium-Activated Neutral Proteinases, CANP, including $\mu$-calpain and m-calpain) are non-lysosomal, neutral intracellular cysteine proteases located in the sarcoplasm that specifically degrade titin, nebulin, and desmin, driving post-mortem aging and tenderization. Cathepsins (B, D, H, L) are lysosomal acid proteases.

Option analysis:

• Calcium activated neutral proteinases: Correct, non-lysosomal calpains responsible for myofibrillar breakdown during aging.
• Cathepsin-B: Lysosomal protease.
• Acid phosphatase: Lysosomal marker enzyme, not a tenderizing protease.
• Cathepsin-D: Lysosomal aspartic protease.