Description
Calpain-1 catalytic subunit is a protein that in humans is encoded by the CAPN1 gene. Calpain is an intracellular protease that requires calcium for its catalytic activity. Two isozymes, CAPN1 (mu-calpain) and CAPN2 (m-calpain), with different calcium requirements, have been identified. Both are heterodimers composed of L (large, catalytic, 82 kD) and S (small, regulatory, 30 kD) subunits. The isozymes share an identical S subunit, with the differences arising from the L subunits. By quantitative RT-PCR, Ueyama et al.(1998) found that expression of Calpain1/2 mRNA was significantly increased in muscle biopsy samples derived from 5 men with progressive muscular dystrophy (e.g., DMD; 310200) and 2 men and 3 women with amyotrophic lateral sclerosis(ALS; 105400) compared with controls. Using cDNA clones as probes, Ohno et al.(1989, 1990) assign CAPNL1 to chromosome 11