 Two enzymes are needed to release tuftsin from immunoglobulin G. First, the spleen enzyme tuftsin-endocarboxypeptidase nicks the heavy chain at the Arg-Glu bond (292-293).The arginine carboxy-terminal is now susceptible to the action of the second enzyme, carboxypeptidase β.The leukokinin-S so nicked is present in tissues and blood, free or bound to outer membrane of the appropriate phagocyte.