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. Mainly expressed in liver. Also detected in lung, stomach, intestine, spleen and kidney. Belongs to the peptidase M14 family.