Dooley D M
Department of Chemistry and Biochemistry, Montana State University, Bozeman 59717, USA.
J Biol Inorg Chem. 1999 Feb;4(1):1-11. doi: 10.1007/s007750050283.
The structure of a new biological redox cofactor-topaquinone (TPQ), the quinone of 2,4,5-trihydroxyphenylalanine-was elucidated in 1990. TPQ is the cofactor in most copper-containing amine oxidases. It is produced by post-translational modification of a strictly conserved active-site tyrosine residue. Recent work has established that TPQ biogenesis proceeds via a novel self-processing pathway requiring only the protein, copper, and molecular oxygen. The oxidation of tyrosine to TPQ by dioxygen is a six-electron process, which has intriguing mechanistic implications because copper is a one-electron redox agent, and dioxygen can function as either a two-electron or four-electron oxidant. This review adopts an historical perspective in discussing the structure and reactivity of TPQ in amine oxidases, and then assesses what is currently understood about the mechanism of the oxidation of tyrosine to produce TPQ. Aspects of the structures and chemistry of related cofactors, such as the Tyr-Cys radical in galactose oxidase and the lysine tyrosylquinone of lysyl oxidase, are also discussed.
1990年，一种新的生物氧化还原辅因子——对苯醌（TPQ），即2,4,5-三羟基苯丙氨酸的醌类化合物的结构得以阐明。TPQ是大多数含铜胺氧化酶中的辅因子。它是由一个严格保守的活性位点酪氨酸残基经翻译后修饰产生的。最近的研究表明，TPQ的生物合成通过一条仅需蛋白质、铜和分子氧的新型自我加工途径进行。二价氧将酪氨酸氧化为TPQ是一个六电子过程，这具有有趣的机理意义，因为铜是单电子氧化还原剂，而二价氧既可以作为双电子氧化剂，也可以作为四电子氧化剂。本文从历史角度讨论了胺氧化酶中TPQ的结构和反应活性，然后评估了目前对酪氨酸氧化生成TPQ的机制的理解。还讨论了相关辅因子的结构和化学方面，如半乳糖氧化酶中的酪氨酸-半胱氨酸自由基和赖氨酰氧化酶中的赖氨酸-酪氨酸醌。
