Calcium-regulated non-lysosomal thiol-protease which catalyze limited proteolysis of substrates involved in cytoskeletal remodeling and signal transduction. Proteolytically cleaves MYOC at 'Arg-226'. Proteolytically cleaves CPEB3 following neuronal stimulation which abolishes CPEB3 translational repressor activity, leading to translation of CPEB3 target mRNAs. Broad endopeptidase specificity. Binds 7 Ca(2+) ions. Activated by 200-1000 micromolar concentrations of calcium and inhibited by calpastatin. Forms a heterodimer with a small (regulatory) subunit (CAPNS1) (PubMed:19020622, PubMed:19020623). Interacts with CPEB3; this leads to cleavage of CPEB3 (By similarity). Translocates to the plasma membrane upon Ca(2+) binding. Ubiquitous. Belongs to the peptidase C2 family.