In biochemistry, the DNA methyltransferase family of enzymes catalyze the transfer of a methyl group to DNA. DNA methylation serves a wide variety of biological functions. All the known DNA methyltransferases use S-adenosyl methionine (SAM) as the methyl donor.
Histone methyltransferases (HMT) are histone-modifying enzymes, that catalyze the transfer of one, two, or three methyl groups to lysine and arginine residues of histone proteins. The attachment of methyl groups occurs predominantly at specific lysine or arginine residues on histones H3 and H4. Two major types of histone methyltranferases exist, lysine-specific and arginine-specific. In both types of histone methyltransferases, S-Adenosyl methionine (SAM) serves as a cofactor and methyl donor group.
The genomic DNA of eukaryotes associates with histones to form chromatin. The level of chromatin compaction depends heavily on histone methylation and other post-translational modifications of histones. Histone methylation is a principal epigenetic modification of chromatin that determines gene expression, genomic stability, stem cell maturation, cell lineage development, genetic imprinting, DNA methylation, and cell mitosis.
S-Adenosyl methionine (SAM), also known under the commercial names of SAMe, SAM-e, or AdoMet, is a common cosubstrate involved in methyl group transfers, transsulfuration, and aminopropylation. Although these anabolic reactions occur throughout the body, most SAM is produced and consumed in the liver. More than 40 methyl transfers from SAM are known, to various substrates such as nucleic acids, proteins, lipids and secondary metabolites. It is made from adenosine triphosphate (ATP) and methionine by methionine adenosyltransferase. SAM was first discovered by Giulio Cantoni in 1952.
Methyltransferases are a large group of enzymes that all methylate their substrates but can be split into several subclasses based on their structural features. The most common class of methyltransferases is class I, all of which contain a Rossmann fold for binding S-Adenosyl methionine (SAM). Class II methyltransferases contain a SET domain, which are exemplified by SET domain histone methyltransferases, and class III methyltransferases, which are membrane associated. Methyltransferases can also be grouped as different types utilizing different substrates in methyl transfer reactions. These types include protein methyltransferases, DNA/RNA methyltransferases, natural product methyltransferases, and non-SAM dependent methyltransferases. SAM is the classical methyl donor for methyltransferases, however, examples of other methyl donors are seen in nature. The general mechanism for methyl transfer is a SN2-like nucleophilic attack where the methionine sulfur serves as the leaving group and the methyl group attached to it acts as the electrophile that transfers the methyl group to the enzyme substrate. SAM is converted to S-Adenosyl homocysteine (SAH) during this process. The breaking of the SAM-methyl bond and the formation of the substrate-methyl bond happen nearly simultaneously. These enzymatic reactions are found in many pathways and are implicated in genetic diseases, cancer, and metabolic diseases. Another type of methyl transfer is the radical S-Adenosyl methionine (SAM) which is the methylation of unactivated carbon atoms in primary metabolites, proteins, lipids, and RNA.
Histone-arginine N-methyltransferase is an enzyme with systematic name S-adenosyl-L-methionine:histone-arginine Nomega-methyltransferase. This enzyme catalyses the following chemical reaction
DNA adenine methylase, (Dam methylase) (also site-specific DNA-methyltransferase (adenine-specific), EC 2.1.1.72, modification methylase, restriction-modification system) is an enzyme that adds a methyl group to the adenine of the sequence 5'-GATC-3' in newly synthesized DNA. Immediately after DNA synthesis, the daughter strand remains unmethylated for a short time. It is an orphan methyltransferase that is not part of a restriction-modification system and regulates gene expression. This enzyme catalyses the following chemical reaction
In enzymology, a calmodulin-lysine N-methyltransferase (EC 2.1.1.60) is an enzyme that catalyzes the chemical reaction
In enzymology, a [cytochrome c]-arginine N-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a [cytochrome-c]-methionine S-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a [myelin basic protein]-arginine N-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a protein-glutamate O-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a protein-histidine N-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a [ribulose-bisphosphate carboxylase]-lysine N-methyltransferase (EC 2.1.1.127) is an enzyme that catalyzes the chemical reaction
In enzymology, a rRNA (adenine-N6-)-methyltransferase (EC 2.1.1.48) is an enzyme that catalyzes the chemical reaction
In enzymology, a tRNA (adenine-N1-)-methyltransferase (EC 2.1.1.36) is an enzyme that catalyzes the chemical reaction
In enzymology, a tRNA (guanine-N2-)-methyltransferase (EC 2.1.1.32) is an enzyme that catalyzes the chemical reaction
In enzymology, a tRNA (guanine-N7-)-methyltransferase (EC 2.1.1.33) is an enzyme that catalyzes the chemical reaction
The SET domain is a protein domain that typically has methyltransferase activity. It was originally identified as part of a larger conserved region present in the Drosophila Trithorax protein and was subsequently identified in the Drosophila Su(var)3-9 and 'Enhancer of zeste' proteins, from which the acronym SET is derived [Su(var)3-9, Enhancer-of-zeste and Trithorax].
23S rRNA (adenine2085-N6)-dimethyltransferase (EC 2.1.1.184, ErmC' methyltransferase, ermC methylase, ermC 23S rRNA methyltransferase, rRNA:m6A methyltransferase ErmC', ErmC', rRNA methyltransferase ErmC' ) is an enzyme with systematic name S-adenosyl-L-methionine:23S rRNA (adenine2085-N6)-dimethyltransferase. This enzyme catalyses the following chemical reaction
[Fructose-bisphosphate aldolase]-lysine N-methyltransferase (EC 2.1.1.259) is an enzyme that catalyses the following chemical reaction
