2024年4月11日发(作者：)

氧甲基转移酶甲基化催化位点

英文回答：

Oxygen methyltransferases (OMTs) are a class of enzymes

that catalyze the transfer of a methyl group from S-

adenosylmethionine (SAM) to an oxygen atom in a substrate.

They play key roles in various biological processes,

including DNA methylation, RNA methylation, and the

biosynthesis of secondary metabolites.

The methyltransferase reaction catalyzed by OMTs

involves two key steps:

1. Substrate Binding and SAM Binding: The enzyme first

binds to the substrate and then to the cofactor SAM. The

substrate binds to the enzyme's active site, which contains

a specific binding pocket that accommodates the substrate

and facilitates its interaction with the enzyme's catalytic

machinery. SAM also binds to the active site, usually in

close proximity to the substrate binding pocket.

2. Methyl Transfer: Once the substrate and SAM are

bound, the enzyme is ready to initiate the methyl transfer

reaction. The mechanism of methyl transfer varies among

different types of OMTs. However, the general steps

involved include the activation of the methyl group in SAM

through nucleophilic attack on the sulfur atom, formation

of a covalent bond between the substrate and the methyl

group, and release of the methylated substrate and SAH.

The methyltransferase activity of OMTs is modulated by

various factors, including:

1. Cofactor Binding: The binding of SAM to the enzyme

is essential for methyltransferase activity. The

dissociation constant for SAM binding can affect the

enzyme's affinity for SAM and its catalytic efficiency.

2. Substrate Specificity: OMTs can exhibit varying

degrees of substrate specificity, depending on the nature

of their active site. Some OMTs have broad substrate

specificity, while others are highly specific for a

particular substrate or group of substrates.

3. Allosteric Regulation: The methyltransferase

activity of OMTs can be regulated by allosteric effectors

that bind to the enzyme outside the active site and

influence its catalytic activity.

中文回答：

氧甲基转移酶甲基化催化位点。

氧甲基转移酶（OMT）是一类催化将甲基从 S-腺苷甲硫氨酸

（SAM）转移到底物中氧原子上的酶。它们在各种生物学过程中扮演

着关键角色，包括 DNA 甲基化、RNA 甲基化和次级代谢产物的生物

合成。

OMT 催化的甲基转移酶反应涉及两个关键步骤：

1. 底物结合和 SAM 结合，该酶首先与底物结合，然后与辅因

子 SAM 结合。底物与该酶的活性位点结合，活性位点含有一个特定

的结合袋，可容纳底物并促进其与该酶催化机制的相互作用。SAM

也与活性位点结合，通常与底物结合袋距离较近。

2. 甲基转移，底物和 SAM 结合后，该酶就能引发甲基转移反

应。甲基转移的机制因不同类型的 OMT 而异。然而，所涉及的普遍

步骤包括，通过亲核攻击硫原子来活化 SAM 中的甲基，在底物和甲

基之间形成共价键，释放甲基化的底物和 SAH。

OMT 的甲基转移酶活性受多种因素调节，包括：

1. 辅因子结合，SAM 与该酶的结合对于甲基转移酶活性至关重

要。SAM 结合的解离常数能影响该酶对 SAM 的亲和力和催化效率。

2. 底物特异性，OMT 可表现出不同程度的底物特异性，具体取

决于其活性位点的性质。一些 OMT 具有广泛的底物特异性，而另一

些 OMT 对特定的底物或底物组高度特异。

3. 变构调节，OMT 的甲基转移酶活性能受变构效应器的调节，

这些效应器结合到活性位点之外的酶并影响其催化活性。