Probably acts as a digestive enzyme. Release of an N-terminal amino acid, Xaa-|-Yaa-, in which Xaa is preferably Leu, but may be other amino acids including Pro although not Arg or Lys, and Yaa may be Pro. Amino acid amides and methyl esters are also readily hydrolyzed, but rates on arylamides are exceedingly low. Binds 2 Zn(2+) ions per subunit. Expressed in the buccal cavity, pharynx, anterior gut and rectum. Belongs to the peptidase M17 family.