Studies on histaminase

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Abstract
A purified prepn. of histaminase was made from hog kidney. Dialysis caused a diminution of the action of this prepn. on histamine, but an increase of its action on various diamines. These effects were due to the loss of flavin-adenine-dinucleotide, which was shown to be present in the enzyme and to reverse both effects. New evidence was presented that when histaminase acted on histamine, the iminazole ring was split in the early stages of the reaction. Expts. with coupled oxidation showed that H2O2 was formed when histaminase acted on histamine. The antihistamine drugs Benadryl, Antergan, Neo-antergan and the prepn. R.P. 3015 did not inhibit histaminase prepns. Partial inhibition was obtained with Antistin and R.P. 3277. It was postulated that histaminase is a flavoprotein with flavin-adenine-dinucleotide as its prosthetic group. The latter depressed the action of histaminase on other diamines.
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