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In the field of enzymology, a betaine-homocysteine S-methyltransferase also known as betaine-homocysteine methyltransferase (BHMT) is a zinc metallo-enzyme that catalyzes the transfer of a methyl group from trimethylglycine and a hydrogen ion from homocysteine to produce dimethylglycine and methionine respectively: [2]
In enzymology, a homocysteine S-methyltransferase (EC 2.1.1.10) is an enzyme that catalyzes the chemical reaction. S-methylmethionine + L-homocysteine 2 L-methionine. Thus, the two substrates of this enzyme are S-methylmethionine and L-homocysteine, and it produces 2 molecules of L-methionine.
Homocysteine (/ ˌ h oʊ m oʊ ˈ s ɪ s t iː n /; symbol Hcy) is a non-proteinogenic α-amino acid. It is a homologue of the amino acid cysteine, differing by an additional methylene bridge (-CH 2-). It is biosynthesized from methionine by the removal of its terminal C ε methyl group.
In humans it is encoded by the MTR gene (5-methyltetrahydrofolate-homocysteine methyltransferase). [ 5 ] [ 6 ] Methionine synthase forms part of the S-adenosylmethionine (SAMe) biosynthesis and regeneration cycle, [ 7 ] and is the enzyme responsible for linking the cycle to one-carbon metabolism via the folate cycle.
Sarcosine/dimethylglycine N-methyltransferase (EC 2.1.1.157, ApDMT, sarcosine-dimethylglycine methyltransferase, SDMT, sarcosine dimethylglycine N-methyltransferase, S-adenosyl-L-methionine:N,N-dimethylglycine N-methyltransferase) is an enzyme with systematic name S-adenosyl-L-methionine:sarcosine(or N,N-dimethylglycine) N-methyltransferase (N,N-dimethylglycine(or betaine)-forming).
Levomefolic acid (INN, also known as L-5-MTHF, L-methylfolate and L-5-methyltetrahydrofolate and (6S)-5-methyltetrahydrofolate, and (6S)-5-MTHF) is the primary biologically active form of folate used at the cellular level for DNA reproduction, the cysteine cycle and the regulation of homocysteine.
S-adenosyl-L-methionine + DNA adenine S-adenosyl-L-homocysteine + DNA 6-methylaminopurine m6A was primarily found in prokaryotes until 2015 when it was also identified in some eukaryotes. m6A methyltransferases methylate the amino group in DNA at C-6 position specifically to prevent the host system to digest own genome through restriction enzymes.
Relevant enzymes include aspartokinase, aspartate-semialdehyde dehydrogenase, homoserine dehydrogenase, homoserine O-transsuccinylase, cystathionine-γ-synthase, Cystathionine-β-lyase (in mammals, this step is performed by homocysteine methyltransferase or betaine—homocysteine S-methyltransferase.)