As more genome sequences are elucidated, there is an increasing need for information about the functions of the millions of proteins they encode. The function of a newly sequenced protein is often estimated by sequence alignment with the sequences of proteins with known functions. However, protein superfamilies can contain members that share significant amino acid sequence and structural homology yet catalyze different reactions or act on different substrates. Some homologous proteins differ by having a second or even third function, called moonlighting proteins. More recently, it was found that most protein superfamilies also include pseudoenzymes, a protein, or a domain within a protein, that has a three‐dimensional fold that resembles a conventional catalytically active enzyme, but has no catalytic activity. In this review, we discuss several examples of protein families that contain enzymes, pseudoenzymes, and moonlighting proteins. It is becoming clear that pseudoenzymes and moonlighting proteins are widespread in the evolutionary tree, and in many protein families, and they are often very similar in sequence and structure to their monofunctional and catalytically active counterparts. A greater understanding is needed to clarify when similarities and differences in amino acid sequences and structures correspond to similarities and differences in biochemical functions and cellular roles. This information can help improve programs that identify protein functions from sequence or structure and assist in more accurate annotation of sequence and structural databases, as well as in our understanding of the broad diversity of protein functions.

中文翻译：

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酶，假酶和月光照蛋白：蛋白质超家族中功能的多样性。

随着更多基因组序列的阐明，人们越来越需要有关其编码的数百万种蛋白质功能的信息。通常通过与具有已知功能的蛋白质序列的序列比对来估计新测序的蛋白质的功能。但是，蛋白质超家族可以包含具有重要氨基酸序列和结构同源性但能催化不同反应或作用于不同底物的成员。一些同源蛋白质的不同之处在于具有第二种或什至第三种功能，称为月光照蛋白。最近，发现大多数蛋白质超家族还包括假酶，一种蛋白质或蛋白质中的一个域，其具有类似于常规催化活性酶的三维折叠，但没有催化活性。在这篇评论中 我们讨论了包含酶，假酶和月光照蛋白的蛋白质家族的几个例子。越来越明显的是，伪酶和月光照蛋白广泛存在于进化树和许多蛋白家族中，它们的序列和结构通常与它们的单功能和催化活性对应物非常相似。需要进一步的理解来阐明氨基酸序列和结构的相似性和差异性何时对应于生化功能和细胞作用的相似性和差异性。这些信息可以帮助改进从序列或结构中识别蛋白质功能的程序，并有助于更准确地注释序列和结构数据库，以及帮助我​​们理解蛋白质功能的广泛多样性。