Probable zinc metalloprotease. Binds 2 Zn(2+) ions per subunit. One is catalytic, whereas the other seems to have a structural role. Down-regulated in testis from patients with maturation arrest (MA) or Sertoli cell-only syndrome (SCOS). Belongs to the peptidase M54 family. An article reported the identification and characterization of this protein as zinc metalloprotease in different tissues; however, this paper was later retracted. Truncated C-terminus.