Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, 04510 México, DF, Mexico.
Chem Biol Interact. 2013 Feb 25;202(1-3):51-61. doi: 10.1016/j.cbi.2012.11.015. Epub 2012 Dec 5.
Within the aldehyde dehydrogenase (ALDH) superfamily, proteins belonging to the ALDH9, ALDH10, ALDH25, ALDH26 and ALDH27 families display activity as ω-aminoaldehyde dehydrogenases (AMADHs). These enzymes participate in polyamine, choline and arginine catabolism, as well as in synthesis of several osmoprotectants and carnitine. Active site aromatic and acidic residues are involved in binding the ω-aminoaldehydes in plant ALDH10 enzymes. In order to ascertain the degree of conservation of these residues among AMADHs and to evaluate their possible relevance in determining the aminoaldehyde specificity, we compared the known amino acid sequences of every ALDH family that have at least one member with known crystal structure, as well as the electrostatic potential surface of the aldehyde binding sites of these structures. Our analyses showed that four or three aromatic residues form a similar "aromatic box" in the active site of the AMADH enzymes, being the equivalents to Phe170 and Trp177 (human ALDH2 numbering) strictly conserved in all of them, which supports their relevance in binding the aminoaldehyde by cation-π interactions. In addition, all AMADHs exhibit a negative electrostatic potential surface in the aldehyde-entrance tunnel, due to side-chain carboxyl and hydroxyl groups or main-chain carbonyl groups. In contrast, ALDHs that have non-polar or negatively charged substrates exhibit neutral or positive electrostatic potential surfaces, respectively. Finally, our comparative sequence analyses revealed that the residues equivalent to Asp121 and Phe170 are highly conserved in many ALDH families irrespective of their substrate specificity-suggesting that they perform a role in catalysis additional or different to binding of the substrate-and that the positions Met124, Cys301, and Cys303 are hot spots changed during evolution to confer aldehyde specificity to several ALDH families.
在醛脱氢酶（ALDH）超家族中，属于 ALDH9、ALDH10、ALDH25、ALDH26 和 ALDH27 家族的蛋白质显示出ω-氨基醛脱氢酶（AMADH）的活性。这些酶参与多胺、胆碱和精氨酸的分解代谢，以及几种渗透保护剂和肉碱的合成。植物 ALDH10 酶的活性部位芳香族和酸性残基参与结合ω-氨基醛。为了确定这些残基在 AMADH 中的保守程度，并评估它们在确定氨基酸醛特异性方面的可能相关性，我们比较了每个至少有一个具有已知晶体结构的成员的 ALDH 家族的已知氨基酸序列，以及这些结构中醛结合位点的静电势表面。我们的分析表明，在 AMADH 酶的活性部位，四个或三个芳香族残基形成一个类似的“芳香族盒”，其中 Phe170 和 Trp177（人 ALDH2 编号）严格保守，这支持了它们通过阳离子-π 相互作用结合氨基酸醛的相关性。此外，所有 AMADH 都在醛入口隧道中表现出负静电势表面，这是由于侧链羧基和羟基或主链羰基。相比之下，具有非极性或带负电荷底物的 ALDH 则分别表现出中性或正静电势表面。最后，我们的比较序列分析表明，许多 ALDH 家族中与 Asp121 和 Phe170 等效的残基高度保守，无论其底物特异性如何-表明它们在催化中发挥作用，除了结合底物之外-并且位置 Met124、Cys301 和 Cys303 是在进化过程中改变的热点，以赋予几种 ALDH 家族醛特异性。
