Calcium-regulated non-lysosomal thiol-protease. Involved in membrane trafficking in the gastric surface mucus cells (pit cells) and may involve the membrane trafficking of mucus cells via interactions with coat protein. Proteolytically cleaves the beta-subunit of coatomer complex (By similarity). . This is the function of CAPN8 (calpain 8, Ensembl gene identifier ENSG00000203697).