May be involved in proteolysis through its threonine endopeptidase activity. May also localize to cytoplasmic membranes. Testis specific. Differentially expressed in some breast cancer tissues. DNA hypomethylation is accompanied by the expression of the gene in the testis. Belongs to the peptidase S1 family. Although related to peptidase S1 family, lacks the conserved active Ser residue in position 310 which is replaced by a Thr.