Calpains are calcium-dependent intracellular nonlysosomal proteases that are believed to participate in signal transduction. In vertebrates, five different calpains have so far been identified, of which three ( u-,Mouse,-, and u/m-calpain) are ubiquitously e, Xenopus/Amphibian,pressed while the other two, nCL-1 (p94) and nCL-2, e, Xenopus/Amphibian,hibit a restricted tissue distribution. Calpain-6 possesses most of the residues conserved in calpain family members but the C-terminal region lacks any homology to the calmodulin-like domain of other vertebrate calpains. Calpain-6 lacks critical active site residues and is not proteolytically active. Calpain-6 is highly e, Xenopus/Amphibian,pressed in the placenta sample.