Protects the body from potent vasoactive and inflammatory peptides containing C-terminal Arg or Lys (such as kinins or anaphylatoxins) which are released into the circulation. Release of a C-terminal basic amino acid, preferentially lysine. Binds 1 zinc ion per subunit. Tetramer of two catalytic chains and two glycosylated inactive chains. Plasma. Expressed in liver. Belongs to the peptidase M14 family.