Localized to zymogen granules, where it functions in trypsinogen activation (By similarity). May indirectly regulate cell motility, cell-cell and cell/extracellular matrix interactions (PubMed:15184879). {ECO:0000250|UniProtKB:P70412, ECO:0000269|PubMed:15184879}. This is the function of Ensembl gene identifier ENSG00000138161 (CUZD1, CUB and zona pellucida like domains 1).