倒相,或β-呋喃果糖苷酶,是广泛分布在植物和微生物中的代谢酶,它们水解蔗糖并从各种底物释放果糖。转化酶是最早发现的酶之一,第一次调查是在19世纪中叶,成为蛋白质合成的主要生化研究中使用的经典模型,活动,和糖蛋白的分泌。然而,直到20年前,这个酶家族的成员在结构上得到了表征,显示具有β-螺旋桨催化域的双模排列,和一个功能未知的β-夹心结构域。从那以后,对相关植物和真菌酶的许多研究表明,它们基本上是单体的。相比之下,到目前为止,该家族中所有已被表征的酵母酶都显示出由非催化结构域介导的复杂寡聚结构,这也涉及底物结合,以及这种组装如何决定每种酶的特定特异性。在这一章中,我们将回顾酵母转化酶的可用结构,以阐明调节寡聚物形成的机制,并将它们与其他报道的二聚体转化酶进行比较,其中寡聚组装没有明显的功能含义。此外,强调了对蓝细菌和植物转化酶中发现的蔗糖α-(1,2)-键具有绝对特异性的新转化酶家族的最新工作。
Invertases, or β-fructofuranosidases, are metabolic enzymes widely distributed among plants and microorganisms that hydrolyze sucrose and release fructose from various substrates. Invertase was one of the earliest discovered enzymes, first investigated in the mid-nineteenth century, becoming a classical model used in the primary biochemical studies on protein synthesis, activity, and the secretion of glycoproteins. However, it was not until 20 years ago that a member of this family of enzymes was structurally characterized, showing a bimodular arrangement with a β-propeller catalytic domain, and a β-sandwich domain with unknown function. Since then, many studies on related plant and fungal enzymes have revealed them as basically monomeric. By contrast, all yeast enzymes in this family that have been characterized so far have shown sophisticated oligomeric structures mediated by the non-catalytic domain, which is also involved in substrate binding, and how this assembly determines the particular specificity of each enzyme. In this chapter, we will review the available structures of yeast invertases to elucidate the mechanism regulating oligomer formation and compare them with other reported dimeric invertases in which the oligomeric assembly has no apparent functional implications. In addition, recent work on a new family of invertases with absolute specificity for the α-(1,2)-bond of sucrose found in cyanobacteria and plant invertases is highlighted.