Intestinal monoamine oxidase: Does it have a role in histamine catabolism?

Publisher Website
Google Scholar
Abstract
The importance of intestinal diamine oxidase in histamine catabolism was proved in several series of experiments. However, intestinal monoamine oxidase might also be involved in histamine degradation either by direct deamination or by the deamination of methylated products. The soluble fraction of intestinal monoamine oxidase was purified and tested for its properties and substrate specificity by three different methods which are described in detail. Using 0.15M phosphate buffer the optimum pH was 7.4–7.6. TheK m values for serotonin and tyramine were 0.2 and 0.3×10−3 M. The most favoured substrates of the enzyme were tyramine, tryptamine and serotonin, but it was not pissible to classify the enzyme as a type A or B monoamine oxidase only by its substrate specificity. Histamine and ring methylated derivatives were not attacked by intestinal monoamine oxidase. This means that in the intestinal mucosa the oxidative pathway of histamine is completely catalysed by diamine oxidase.