Deciphering the regulatory and catalytic mechanisms of an unusual SAM-dependent enzyme
Deciphering the regulatory and catalytic mechanisms of an unusual SAM-dependent enzyme
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破译一种不寻常的 SAM 依赖性酶的调节和催化机制
DOI：
10.1038/s41392-019-0052-y
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发表时间：
2019-05-24
影响因子：
39.3
通讯作者：
Cheng, Wei
中科院分区：
文献类型：
--
作者：
Sun, Qiu;Hu, Yuehong;Cheng, Wei
S-腺苷-1-蛋氨酸依赖的酶调节所有生物体中各种与疾病相关的行为。最近，LePorin生物合成酶LepI被报道在LePorin生物合成中催化周环反应，LepI是一种依赖于SAM的酶，然而LepI激活和催化的机制尚不清楚。本研究旨在探讨LepI的分子机制。在这里，我们报道了LepI与腺苷/5‘-脱氧-5’-(甲硫基)腺苷(MTA)、S-腺苷-同型半胱氨酸(SAH)以及腺苷/底物结合的晶体结构。结构和生化分析表明，MTA或SAH抑制该酶的活性，而SAM激活该酶的活性。对LepI底物结合结构的分析表明，这种酶促逆转Claisen重排主要由活性中心周围的三个关键极性残基His133、Arg197、Arg295驱动，并由SAM辅助，但机制尚不清楚。目前的研究表明，独特的SAM依赖酶LepI调控和催化的独特机制，不仅加强了当前对基本生化催化的理解，而且为SAM依赖的酶特异性小分子的设计提供了新的见解。
S-adenosyl-1-methionine (SAM)-dependent enzymes regulate various disease-related behaviors in all organisms. Recently, the leporin biosynthesis enzyme LepI, a SAM-dependent enzyme, was reported to catalyze pericyclic reactions in leporin biosynthesis; however, the mechanisms underlying LepI activation and catalysis remain unclear. This study aimed to investigate the molecular mechanisms of LepI. Here, we reported crystal structures of LepI bound to SAM/ 5'-deoxy-5'-(methylthio) adenosine (MTA), S-adenosyl-homocysteine (SAH), and SAM/ substrate states. Structural and biochemical analysis revealed that MTA or SAH inhibited the enzyme activities, whereas SAM activated the enzyme. The analysis of the substrate-bound structure of LepI demonstrated that this enzymatic retro-Claisen rearrangement was primarily driven by three critical polar residues His133, Arg197, Arg295 around the active site and assisted by SAM with unclear mechanism. The present studies indicate that the unique mechanisms underlying regulatory and catalysis of the unusual SAM-dependent enzyme LepI, not only strengthening current understanding of the fundamentally biochemical catalysis, but also providing novel insights into the design of SAM-dependent enzyme-specific small molecules.