calpaïne
Calpains are a family of calcium-dependent cysteine proteases found in eukaryotes. They play crucial roles in various cellular processes, including cell growth, differentiation, apoptosis, and muscle contraction. Calpains are characterized by their dependence on calcium ions for activation and their unique catalytic mechanism involving a cysteine residue. The calpain family is broadly divided into two main types: ubiquitous calpains, found in most cell types, and non-ubiquitous calpains, which have more restricted tissue distribution. Activation typically involves the binding of calcium ions to specific domains within the calpain structure, leading to a conformational change that exposes the active site. Dysregulation of calpain activity has been implicated in a number of diseases, including neurodegenerative disorders, muscular dystrophies, and cancer. Research into calpain function and inhibition continues to be an active area of investigation for therapeutic development.