Calpain-1 catalytic subunit and Calpain-2 catalytic subunit (CAPN1 (for Calpain-1); CAPN2 (for Calpain-2))

Calpain-1 catalytic subunit (gene: CAPN1) and calpain-2 catalytic subunit are large, homologous proteins that serve as the catalytic cores of the proteases calpain-1 (μ-calpain) and calpain-2 (m-calpain), respectively[3][6][7]. Calpains are intracellular, non-lysosomal, calcium-dependent cysteine proteases that function as heterodimers consisting of a large catalytic subunit (CAPN1 or CAPN2) and a small regulatory subunit (CAPNS1)[2][5]. Upon calcium binding, they catalyze limited proteolysis of cytoskeletal and signaling proteins, regulating processes such as cell migration, survival, apoptosis, and signal transduction[3][6][7]. Calpains participate in both physiological signaling and, when dysregulated, pathological processes including cancer, neurodegeneration, and cardiac disease[2][4]. While inhibitors exist for research, there are currently no clinically approved, highly selective calpain-1 or calpain-2 inhibitors, partly due to the challenge of selectively targeting such fundamental and broadly expressed enzymes[2].\n\nNote: The name "Calpain 1/2 catalytic subunits" describes two closely related enzymes; for most structured data, these are best represented as "Calpain-1 catalytic subunit" and "Calpain-2 catalytic subunit" individually, with CAPN1 and CAPN2 as their standard gene/protein abbreviations[2][3][6][7].

Other names

Mu-type calpainCANP1Calpain small subunit 1m-CalpainCANP2

Inhibition of Ca²⁺-dependent protease activity\nAllosteric inhibition disrupts heterodimerization with the common regulatory subunit (CAPNS1)[2]\nBlockade of the active site cysteine impedes substrate proteolysis