Enables endopeptidase inhibitor activity. Acts upstream of or within negative regulation of endopeptidase activity. Predicted to be located in several cellular components, including cornified envelope; extracellular space; and nucleoplasm. Predicted to be active in cytosol. Human ortholog(s) of this gene implicated in peeling skin syndrome. Orthologous to human CSTA (cystatin A). [provided by Alliance of Genome Resources, Apr 2022]