STRUCTURE AND PHYSIOLOGY OF CALPAIN, AN ENIGMATIC PROTEASE

Calpain is one of the most extensively studied proteinases (1). Althou gh its enzymatic and structural properties have been well characterize d, neither the structure-function relationship nor physiological funct ions are completely understood, In recent years, increasing numbers of molecules showing sequence similarity to calpain have been identified and the concept of a ''calpain super family'' has become general (2, 3). The term ''calpain'' originally meant a Ca2+-activated, neutral, a nd intracellular cysteine proteinase, although a proteinase domain sim ilar to that of calpain is a prerequisite for a member of the ''calpai n super family'' (4, 5). The molecular diversity of calpain has attrac ted interest to its structural and functional transition during evolut ion. Here we describe the state of current knowledge, progress, and cl ues to the next phase of calpain research. (C) 1998 Academic Press.