DIAMINE OXIDASE - AN OVERVIEW OF HISTORICAL, BIOCHEMICAL AND FUNCTIONAL-ASPECTS

This article is a review of the historical, biochemical, and functiona l aspects of the enzyme diamine oxidase (DAO). The amine oxidase DAO, formerly called histaminase, is found in various tissues, but is espec ially active in the intestinal mucosa. Its function is the oxidative d eaminating of several polyamines, essential substances for cell prolif eration. DAO is thus a regulating enzyme in rapidly proliferating tiss ues such a bone marrow and intestinal mucosa. Results from several stu dies have demonstrated that both ornithine decarboxylase (ODC) and DAO activity rise during adaptive hyperplasia seen after small bowel rese ction. The ODC-dependent increase in polyamine content and subsequent increase in cell proliferative activity is probably downregulated loca lly in the villus tip by the increased DAO activity. DAO is normally p resent in very small amounts in the circulation and its basal plasma l evels are positively correlated with the maturity and integrity of the intestinal mucosa. After intravenous administration of heparin, DAO i s released from its capillary binding sites in the lamina propria into the peripheral circulation. Measurement of postheparin DAO release en hances its sensitivity and is now extensively studied to assess its va lue as follow-up or screening test for several enteropathies. Measurin g basal as well as postheparin DAO levels has potential relevance foll owing small bowel transplantation. Rejection of the small bowel graft leads to mucosal damage, which could conceivably lead to changes in DA O activity.