Calpain I, II small subunit p30, mAb (28F3)

The calpains are calcium-dependent cysteine proteases that are widely expressed in mammalian systems. Both m-calpain (calpain II) and μ-calpain (calpain I) are composed of two subunits (80 kDa and 30 kDa). Whereas the small subunit is common to both enzymes, the larger catalytic subunits are different and exhibit distinct calcium ion requirements. m-Calpain requires millimolar levels of Ca²⁺, and μ-calpain is active at micromolar concentrations of Ca²⁺. In addition to the ubiquitously expressed m- and μ-calpains, some tissue-specific calpains have been identified.