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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]
Thus, the two substrates of this enzyme are S-methylmethionine and L-homocysteine, and it produces 2 molecules of L-methionine. This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:L-homocysteine S ...
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.
These enzymes use S-adenosylmethionine as a methyl donor and contain several highly conserved structural features between the three forms; these include the S-adenosylmethionine binding site, a vicinal proline-cysteine pair which forms a thiolate anion important for the reaction mechanism, and the cytosine substrate binding pocket.
DNMT1 is the most abundant DNA methyltransferase in mammalian cells, and considered to be the key maintenance methyltransferase in mammals. It predominantly methylates hemimethylated CpG di-nucleotides in the mammalian genome. The recognition motif for the human enzyme involves only three of the bases in the CpG dinucleotide pair: a C on one ...
Another example of historical significance relating to transferase is the discovery of the mechanism of catecholamine breakdown by catechol-O-methyltransferase. This discovery was a large part of the reason for Julius Axelrod’s 1970 Nobel Prize in Physiology or Medicine (shared with Sir Bernard Katz and Ulf von Euler). [16]
The S-methyl-L-cysteine residue irreversibly inactivates the protein, allowing only one transfer for each protein. This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is DNA-6-O-methylguanine:[protein]-L-cysteine S-methyltransferase.
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).