Histaminase (diamine oxidase) activity in human tumors: an expression of a mature genome.

High histaminase [amine:oxygen oxidoreductase (deaminating) (pyridoxal-containing), EC 1.4.3.6] activity is found in certain human tumors and in the placenta of most mammals. The present study explores the relationship of tumor histaminase to histaminases found in placenta and other human, pig, and rat tissues. The electrophoretic mobility and Michaelis constants for the deamination of histimine and putrescine were identical for histaminases from human placenta and from medullary thyroid carcinoma. An antibody was raised in rabbits against human placental histaminase that was highly purified by a new affinity procedure. In separate studies, using inhibitory concentrations of antibody and a second antibody precipitation technique, identical patterns of immunoreactivity were found for histaminases from human placenta, kidney, medullary thyroid carcinoma, and small cell lung carcinoma; human intestinal histaminase crossreacted well but less strongly than did enzymes from these other tissues. Histaminases from pig kidney, pig intestine, and rat intestine showed no crossreaction; histaminases from rat thymus and adrenal gland showed minimal crossreactivity. The findings suggest that placental histaminase activity is not a unique product of a fetal or trophoblastic genome. The presence of histaminase in malignancies does not appear to be an example of ectopic tumor production of a placental trophoblastic protein.