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.
A capping enzyme (CE) is an enzyme that catalyzes the attachment of the 5' cap to messenger RNA molecules that are in the process of being synthesized in the cell nucleus during the first stages of gene expression. The addition of the cap occurs co-transcriptionally, after the growing RNA molecule contains as little as 25 nucleotides. The enzymatic reaction is catalyzed specifically by the phosphorylated carboxyl-terminal domain (CTD) of RNA polymerase II. The 5' cap is therefore specific to RNAs synthesized by this polymerase rather than those synthesized by RNA polymerase I or RNA polymerase III. Pre-mRNA undergoes a series of modifications - 5' capping, splicing and 3' polyadenylation before becoming mature mRNA that exits the nucleus to be translated into functional proteins and capping of the 5' end is the first of these modifications. Three enzymes, RNA triphosphatase, guanylyltransferase, and methyltransferase are involved in the addition of the methylated 5' cap to the mRNA.
N-Acetylserotonin O-methyltransferase, also known as ASMT, is an enzyme which catalyzes the final reaction in melatonin biosynthesis: converting Normelatonin to melatonin. This reaction is embedded in the more general tryptophan metabolism pathway. The enzyme also catalyzes a second reaction in tryptophan metabolism: the conversion of 5-hydroxy-indoleacetate to 5-methoxy-indoleacetate. The other enzyme which catalyzes this reaction is n-acetylserotonin-o-methyltransferase-like-protein.
In enzymology, a 7-methylxanthosine synthase is an enzyme that catalyzes the chemical reaction
Guanidinoacetate N-methyltransferase is an enzyme that catalyzes the chemical reaction and is encoded by gene GAMT located on chromosome 19p13.3.
In enzymology, a mRNA (2'-O-methyladenosine-N6-)-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a mRNA (nucleoside-2'-O-)-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a tRNA (cytosine-5-)-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a tRNA (guanine-N1-)-methyltransferase (EC 2.1.1.31) 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
In enzymology, a tRNA (uracil-5-)-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a mRNA guanylyltransferase is an enzyme that catalyzes the chemical reaction
Protein-L-isoaspartate(D-aspartate) O-methyltransferase is an enzyme that in humans is encoded by the PCMT1 gene.
Dimethyladenosine transferase 1, mitochondrial; Transcription factor B1, mitochondrial is a mitochondrial enzyme that in is encoded by the TFB1M gene.
mRNA-capping enzyme is a protein that in humans is encoded by the RNGTT gene.
Protein arginine N-methyltransferase 6 is an enzyme that in humans is encoded by the PRMT6 gene.
N6-adenosine-methyltransferase 70 kDa subunit (METTL3) is an enzyme that in humans is encoded by the METTL3 gene.
16S rRNA (guanine527-N7)-methyltransferase (EC 2.1.1.170, ribosomal RNA small subunit methyltransferase G, 16S rRNA methyltransferase RsmG, GidB, rsmG (gene)) is an enzyme with systematic name S-adenosyl-L-methionine:16S rRNA (guanine527-N7)-methyltransferase. This enzyme catalyses the following chemical reaction
16S rRNA (guanine1405-N7)-methyltransferase (EC 2.1.1.179, methyltransferase Sgm, m7G1405 Mtase, Sgm Mtase, Sgm, sisomicin-gentamicin methyltransferase, sisomicin-gentamicin methylase, GrmA, RmtB, RmtC, ArmA) is an enzyme with systematic name S-adenosyl-L-methionine:16S rRNA (guanine1405-N7)-methyltransferase. This enzyme catalyses the following chemical reaction
23S rRNA (guanine2069-N7)-methyltransferase (EC 2.1.1.264, rlmK (gene), 23S rRNA m7G2069 methyltransferase) is an enzyme with systematic name S-adenosyl-L-methionine:23S rRNA (guanine2069-N7)-methyltransferase. This enzyme catalyses the following chemical reaction
