In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These terms are commonly used in chemistry, biochemistry, soil science, and the biological sciences.
Methionine synthase also known as MS, MeSe, MTR is responsible for the regeneration of methionine from homocysteine. In humans it is encoded by the MTR gene (5-methyltetrahydrofolate-homocysteine methyltransferase). Methionine synthase forms part of the S-adenosylmethionine (SAMe) biosynthesis and regeneration cycle, and is the enzyme responsible for linking the cycle to one-carbon metabolism via the folate cycle. There are two primary forms of this enzyme, the Vitamin B12 (cobalamin)-dependent (MetH) and independent (MetE) forms, although minimal core methionine synthases that do not fit cleanly into either category have also been described in some anaerobic bacteria. The two dominant forms of the enzymes appear to be evolutionary independent and rely on considerably different chemical mechanisms. Mammals and other higher eukaryotes express only the cobalamin-dependent form. In contrast, the distribution of the two forms in Archaeplastida (plants and algae) is more complex. Plants exclusively possess the cobalamin-independent form, while algae have either one of the two, depending on species. Many different microorganisms express both the cobalamin-dependent and cobalamin-independent forms.
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.
Dihydropteroate synthase is an enzyme classified under EC 2.5.1.15. It produces dihydropteroate in bacteria, but it is not expressed in most eukaryotes including humans. This makes it a useful target for sulfonamide antibiotics, which compete with the PABA precursor.
Glutamate formimidoyltransferase is a methyltransferase enzyme which uses tetrahydrofolate as part of histidine catabolism. It catalyses two reactions:
In enzymology, sarcosine dehydrogenase (EC 1.5.8.3) is a mitochondrial enzyme that catalyzes the chemical reaction N-demethylation of sarcosine to give glycine. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donor with other acceptors. The systematic name of this enzyme class is sarcosine:acceptor oxidoreductase (demethylating). Other names in common use include sarcosine N-demethylase, monomethylglycine dehydrogenase, and sarcosine:(acceptor) oxidoreductase (demethylating). Sarcosine dehydrogenase is closely related to dimethylglycine dehydrogenase, which catalyzes the demethylation reaction of dimethylglycine to sarcosine. Both sarcosine dehydrogenase and dimethylglycine dehydrogenase use FAD as a cofactor. Sarcosine dehydrogenase is linked by electron-transferring flavoprotein (ETF) to the respiratory redox chain. The general chemical reaction catalyzed by sarcosine dehydrogenase is:
In enzymology, a 5-methyltetrahydropteroyltriglutamate—homocysteine S-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, an amine N-methyltransferase is an enzyme that is ubiquitously present in non-neural tissues and that catalyzes the N-methylation of tryptamine and structurally related compounds.
In enzymology, a glycine N-methyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a methylenetetrahydrofolate-tRNA-(uracil-5-)-methyltransferase (EC 2.1.1.74) is an enzyme that catalyzes the chemical reaction
In enzymology, a thioether S-methyltransferase is an enzyme that catalyzes the chemical reaction.
In enzymology, a thymidylate synthase (FAD) (EC 2.1.1.148) is an enzyme that catalyzes the chemical reaction
In enzymology, a 3-methyl-2-oxobutanoate hydroxymethyltransferase (EC 2.1.2.11) is an enzyme that catalyzes the chemical reaction
In enzymology, a glycine formimidoyltransferase is an enzyme that catalyzes the chemical reaction
In enzymology, a methionyl-tRNA formyltransferase (EC 2.1.2.9) is an enzyme that catalyzes the chemical reaction
In enzymology, a phosphoribosylaminoimidazolecarboxamide formyltransferase, also known by the shorter name AICAR transformylase, is an enzyme that catalyzes the chemical reaction
In enzymology, a formate—tetrahydrofolate ligase is an enzyme that catalyzes the chemical reaction
N-methyltransferase may refer to:
5-methyltetrahydrofolate:corrinoid/iron-sulfur protein Co-methyltransferase is an enzyme with systematic name 5-methyltetrahydrofolate:corrinoid/iron-sulfur protein methyltransferase. This enzyme catalyses the following chemical reaction
Riboflavin-responsive exercise intolerance is a rare disorder caused by mutations of the SLC25A32 gene that encodes the mitochondrial folate transporter. Patients suffer from exercise intolerance and may have disrupted motor function.
