Interaction of N‐(2‐Nitro‐4‐Azidophenyl)‐Serotonin with Two Types of Monoamine Oxidase in Rat Brain

Publisher Website
Google Scholar
Abstract
The effects of N-(2-nitro-4-azidophenyl) serotonin [5-hydroxytryptamine] (NAP-5-HT) on types A and B monoamine oxidase (MAO) in rat brain cortex were studied. In the dark this compound acted as a competitive inhibitor for both types A and B MAO (Ki values of 0.19 .mu.M and 0.21 .mu.M for types A and B MAO, respectively). Upon photolysis, NAP-5-HT became an irreversible inhibitor for only type B MAO. A 50% inhibition was obtained by irradiation of the enzyme in the presence of 35 nM NAP-5-HT. Furthermore the inhibition of type B MAO could be protected by including its substrate phenylethylamine during the irradiation. Under the same photolytic conditions photodependent inhibition of type A MAO by NAP-5-HT was not clearly observed. These results provide further evidence that there is a fundamental difference in the active site of the 2 types of MAO in brain. NAP-5-HT may be a useful photoaffinity probe for characterizing the active site of type B MAO.