Chen S, Shih J C, Xu Q P
J Neurochem. 1984 Dec;43(6):1680-7. doi: 10.1111/j.1471-4159.1984.tb06095.x.
The effects of N-(2-nitro-4-azidophenyl) serotonin (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 microM and 0.21 microM 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 two types of MAO in brain. NAP-5-HT may be a useful photoaffinity probe for characterizing the active site of type B MAO.
研究了N-(2-硝基-4-叠氮苯基)血清素（NAP-5-HT）对大鼠脑皮层中A、B型单胺氧化酶（MAO）的影响。在黑暗中，该化合物对A、B型MAO均起竞争性抑制剂作用（A、B型MAO的Ki值分别为0.19微摩尔和0.21微摩尔）。光解后，NAP-5-HT仅成为B型MAO的不可逆抑制剂。在35纳摩尔NAP-5-HT存在下照射酶可实现50%的抑制。此外，在照射过程中加入其底物苯乙胺可保护B型MAO的抑制作用。在相同光解条件下，未明显观察到NAP-5-HT对A型MAO的光依赖性抑制。这些结果进一步证明，脑中两种类型MAO的活性位点存在根本差异。NAP-5-HT可能是用于表征B型MAO活性位点的有用光亲和探针。
