Enzymes of the chalcone synthase superfamily from plants and microorganisms

植物次生代谢产物黄酮类化合物（抗紫外线）、异黄酮类化合物（根瘤菌结瘤）、花青素（花的颜色）、抗菌素等都是查尔酮合成酶（CHS）超家族成员合成的聚酮类化合物。这些酶很小（约42 kDa亚基的同型二聚体），但非常复杂，在一个活性位点催化多步反应。因此，它们为其他多组分聚酮合成酶提供了一个很好的模型，这些多组分聚酮合成酶负责生物合成各种有用的天然产物，包括抗生素、免疫抑制剂和抗癌药物。近年来对CHS及其相关酶的结构和机理的研究，对CHS超家族的酶机制和生物合成多功能性的分子基础有了深入的了解。Stilbene synthase是该超家族的另一代表成员，由于其抗真菌活性和许多有益健康的作用，在转基因作物开发中受到了广泛的关注。利用未开发的生物有机化学方法对sts催化的环化反应进行机理研究，将为通过代谢工程操纵聚酮生物合成提供急需的见解。对类似chs的酶的研究已经在进行中，这些酶来自一种蓝细菌、一种固氮细菌、一种苔藓和一种原始植物马尾草。这些研究结果将有助于更好地理解植物和微生物中酶家族的进化和代谢途径。最后，花药特异性CHSs的苔藓同源性可能为了解植物雄性生殖过程提供见解。

Plant secondary metabolites such as flavonoids (UV protection), isoflavonoids (Rhizobium nodulation), anthocyanins (floral color), and antimicrobial phytoalexins are all derived from polyketides synthesized by the members of chalcone synthase (CHS) superfamily. These enzymes are small (homodimer of ~42 kDa subunits), yet remarkably complex enzymes and catalyze multiple-step reactions at a single active site. Thus, they provide a good model for other multi-component polyketide synthases, which are responsible for biosynthesis of a variety of useful natural products including antibiotics, immunosuppressants and anticancer agents. Recent structural and mechanistic studies on CHS and related enzymes have yielded insights into enzyme mechanisms and the molecular basis of biosynthetic versatility of the CHS superfamily. Stilbene synthase, another representative member of the superfamily, has attracted much attention in transgenic crop development due to the antifungal activity and a number of beneficial health effects of stilbenes. The proposed mechanistic study on the STS-catalyzed cyclization reaction using unexplored bioorganic chemical approaches will provide much needed insight that should prove valuable in the manipulation of polyketide biosynthesis through metabolic engineering. Already underway are studies on CHS-like enzymes from a cyanobacterium, a nitrogen-fixing bacterium, a moss, and a primitive plant, horsetail. Results obtained from these studies will lead to a better understanding of the evolution of enzyme family and metabolic pathway in plants and microorganisms. Finally, the moss homologue of anther-specific CHSs may provide insights into the poorly understood process of plant male fertility.