Catalytic turnover of substrate benzylamines by the quinone-dependent plasma amine oxidase leads to H2O2-dependent inactivation: evidence for generation of a cofactor-derived benzoxazole.
Catalytic turnover of substrate benzylamines by the quinone-dependent plasma amine oxidase leads to H2O2-dependent inactivation: evidence for generation of a cofactor-derived benzoxazole.
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醌依赖性血浆胺氧化酶对底物苯甲胺的催化周转导致 H2O2 依赖性失活：生成辅因子衍生的苯并恶唑的证据。
DOI：
10.1021/bi002118y
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发表时间：
2001
期刊：
影响因子：
2.9
通讯作者：
Sayre,LM
中科院分区：
文献类型：
--
作者：
Lee,Y;Shepard,E;Smith,J;Dooley,DM;Sayre,LM
牛血浆胺氧化酶（BPAO）与苄胺和各种取代的类似物孵育导致时间依赖性失活，这是由于在与过氧化氢酶共孵育提供保护的基础上，h2o2转化产物的积累。它的失活机制不同于h2o2本身的失活机制，需要更高的浓度。使用2,4,5-三羟基苯丙氨酸醌（TPQ）辅助因子模型进行的溶液研究表明，由于产品希夫碱的二氢苯并恶唑互变异构体氧化而导致催化活性丧失，这与苯甲醛产品的水解释放相竞争。得到的稳定的苯并恶唑表现出依赖于苄胺取代基性质的特征吸收。对于苯并恶唑本身，模型苯并恶唑在313 nm处吸收，处于酶的强吸收区域，而对于4-硝基苯并恶唑，模型苯并恶唑的吸收有足够的红移（365 nm），可以在酶的背景吸收之上识别。4-硝基苄胺使BPAO失活时，在480 nm处TPQ阴离子的静息吸收丧失，同时在360 nm附近产生新的吸收。失活酶的共振拉曼光谱与模型4-硝基苄胺衍生的苯并恶唑的共振拉曼光谱非常接近。另外两种被检测的哺乳动物酶，马血浆胺氧化酶和人肾胺氧化酶，也观察到底物依赖性失活。过氧化氢酶在这些情况下也提供了完全的保护。如果允许产物h2o2积累，苯并恶唑的形成可能是体外正常底物使醌依赖胺氧化酶失活的常见机制。更重要的是，结果表明苯并恶唑失活途径可能具有重要的生理作用，并可能影响细胞中胺氧化酶和过氧化氢酶的分布。
Incubation of bovine plasma amine oxidase (BPAO) with benzylamine and variousp-substituted analogues results in a time-dependent inactivation that is attributable to buildup of the H2O2-turnover product on the basis of protection afforded by coincubation with catalase. The mechanism of inactivation is distinct from that effected by H2O2itself, which requires higher concentrations. Solution studies using models for the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor reveal a loss of catalytic activity arising from oxidation of the dihydrobenzoxazole tautomer of the product Schiff base, that competes with hydrolytic release of benzaldehyde product. The resulting stable benzoxazole exhibits a characteristic absorption depending on the nature of the benzylaminep-substituent. For benzylamine itself, the model benzoxazole absorbs at 313 nm, in an area of strong absorption by the enzyme, whereas for 4-nitrobenzylamine, the absorption of the model benzoxazole is sufficiently red-shifted (at 365 nm) to be discerned above the background enzyme absorption. Inactivation of BPAO by 4-nitrobenzylamine is accompanied by loss of the resting TPQ anion absorption at 480 nm concomitant with generation of a new absorption near 360 nm. Resonance Raman spectra of the inactivated enzyme show a close correspondence with those for the model 4-nitrobenzylamine-derived benzoxazole. Substrate-dependent inactivation is also observed for the other two mammalian enzymes examined, equine plasma amine oxidase and human kidney amine oxidase. Catalase provides complete protection in these instances as well. Benzoxazole formation may constitute a common mechanism of inactivation of quinone-dependent amine oxidases by normal substrates in vitro if the product H2O2is permitted to accumulate. More importantly, the results suggest that the benzoxazole inactivation pathway may be important physiologically and may have influenced the distribution of amine oxidases and catalase in cells.