Abstract：
Enzymes can usually be unambiguously assigned to one of seven classes specifying the basic chemistry of their catalyzed reactions. Less frequently, two or more reaction classes are catalyzed by a single enzyme within one active site. Two examples are an isomerohydrolase and an isomero-oxygenase that catalyze isomerization-coupled reactions crucial for production of vision-supporting 11-cis-retinoids. In these enzymes, isomerization is obligately paired and mechanistically intertwined with a second reaction class. A handful of other enzymes carrying out similarly coupled isomerization reactions have been described, some of which have been subjected to detailed structure-function analyses. Herein we review these rarefied enzymes, focusing on the mechanistic and structural basis of their reaction coupling with the goal of revealing catalytic commonalities.
摘要：
酶通常可以明确地指定为七类中的一类，说明其催化反应的基本化学。不那么频繁,两个或更多个反应类别由一个活性位点内的单个酶催化。两个例子是异构水解酶和异构加氧酶，它们催化对于视觉支持的11-顺式类维生素A的生产至关重要的异构化偶联反应。在这些酶中，异构化是强制性配对的，并在机械上与第二类反应交织在一起。已经描述了进行类似的偶联异构化反应的少数其他酶，其中一些已经过详细的结构功能分析。在这里，我们回顾了这些稀有的酶，重点研究其反应耦合的机理和结构基础，目的是揭示催化共性。
