Calpains constitute a family of intracellular calcium-dependent cysteine proteases. There are eight members in this superfamily. They consist of a variable 80 kDa subunit and an invariant 30 kDa subunit. This calpain protein appears to have protease activity and calcium-binding ability. A similar mouse protein may play a functional role in spermatogenesis and in the regulation of calcium-dependent signal transduction events during meiosis.