Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, Münster, Germany.
Microbiol Mol Biol Rev. 2013 Jun;77(2):277-321. doi: 10.1128/MMBR.00010-13.
Long-chain-length hydrophobic acyl residues play a vital role in a multitude of essential biological structures and processes. They build the inner hydrophobic layers of biological membranes, are converted to intracellular storage compounds, and are used to modify protein properties or function as membrane anchors, to name only a few functions. Acyl thioesters are transferred by acyltransferases or transacylases to a variety of different substrates or are polymerized to lipophilic storage compounds. Lipases represent another important enzyme class dealing with fatty acyl chains; however, they cannot be regarded as acyltransferases in the strict sense. This review provides a detailed survey of the wide spectrum of bacterial acyltransferases and compares different enzyme families in regard to their catalytic mechanisms. On the basis of their studied or assumed mechanisms, most of the acyl-transferring enzymes can be divided into two groups. The majority of enzymes discussed in this review employ a conserved acyltransferase motif with an invariant histidine residue, followed by an acidic amino acid residue, and their catalytic mechanism is characterized by a noncovalent transition state. In contrast to that, lipases rely on completely different mechanism which employs a catalytic triad and functions via the formation of covalent intermediates. This is, for example, similar to the mechanism which has been suggested for polyester synthases. Consequently, although the presented enzyme types neither share homology nor have a common three-dimensional structure, and although they deal with greatly varying molecule structures, this variety is not reflected in their mechanisms, all of which rely on a catalytically active histidine residue.
长链疏水酰基残基在许多重要的生物结构和过程中起着至关重要的作用。它们构成了生物膜的内部疏水层，被转化为细胞内储存化合物，并被用来修饰蛋白质性质或作为膜锚定物发挥功能，这里仅列举了其中一些功能。酰基辅酶 A 通过酰基转移酶或转酰基酶转移到各种不同的底物上，或者聚合形成亲脂性储存化合物。脂肪酶是另一类处理脂肪酸链的重要酶；然而，从严格意义上讲，它们不能被视为酰基转移酶。这篇综述详细调查了广泛的细菌酰基转移酶，并比较了不同的酶家族在其催化机制方面的差异。基于已研究或假设的机制，大多数酰基转移酶可分为两类。本文讨论的大多数酶都采用保守的酰基转移酶基序，其中包含一个不变的组氨酸残基，后面跟着一个酸性氨基酸残基，其催化机制的特点是非共价过渡态。与之相反，脂肪酶依赖于完全不同的机制，该机制采用催化三联体，并通过形成共价中间产物来发挥作用。这类似于已提出的聚酯合酶的机制。因此，尽管所呈现的酶类型既没有共享同源性，也没有共同的三维结构，并且它们处理的分子结构差异很大，但这种多样性并没有反映在它们的机制中，所有这些机制都依赖于催化活性的组氨酸残基。
