Releases C-terminal Arg and Lys from polypeptides. Binds 2 Zn(2+) ions per subunit. Isoform 1 is widely expressed with highest levels in the hippocampus, spinal cord, atrium, colon, testis and ovaries. Detected in the liver of females but not males. Isoform 2 is not detected in brain or lung. Up-regulated by exposure to prolactin or interleukin-2. There are 3 carboxypeptidase-like domains. Only the first two domains seem to have kept a catalytic activity. Belongs to the peptidase M14 family.