Calpains are ubiquitous, well-conserved family of calcium-dependent, cysteine proteases. The calpain proteins are heterodimers consisting of an invariant small subunit and variable large subunits. The large subunit possesses a cysteine protease domain, and both subunits possess calcium-binding domains. Calpains have been implicated in neurodegenerative processes, as their activation can be triggered by calcium influx and oxidative stress. The protein encoded by this gene is expressed predominantly in stomach and small intestine and may have specialized functions in the digestive tract. This gene is thought to be associated with gastric cancer. Multiple alternatively spliced transcript variants encoding different isoforms have been found for this gene.CAPN9 (Calpain 9) is a Protein Coding gene. Diseases associated with CAPN9 include Gastric Cancer. Among its related pathways are Degradation of the extracellular matrix and Arrhythmogenic right ventricular cardiomyopathy (ARVC). GO annotations related to this gene include calcium ion binding and calcium-dependent cysteine-type endopeptidase activity. An important paralog of this gene is CAPN3.