Synonyms: a methylated methyl acceptor
|Superclasses:||an acceptor → a methyl group donor|
A methyl group donor is a compound that can donate a methyl group to another compound in a reaction catalyzed by enzymes that belong to the methyltransferase group. Prior to donating the methyl group the compound is a methylated methyl donor and after donating it the compound is a demethylated methyl donor.
Since methylation reactions are sometimes reversible, the distinction between a methyl group donor and a methyl group acceptor is not always determined by the actual chemical entity, but by the role it plays in a particular reaction. However, some compounds are often used as methyl group donors by the methyltransferases in reactions that are physiologically unidirectional.
By far, the most common methyl group donor in biology is S-adenosyl-L-methionine. However, other methyl donors exist, including methanol, N5-methyl tetrahydrofolate, N5-methyltetrahydromethanopterin, methylamine, dimethylamine, trimethylamine, and methanethiol.
This particular entry is used when the identity of the methyl group donor (or acceptor) is not known or cannot be defined.
Reactions known to consume the compound:
Reactions known to produce the compound:
autoinducer AI-2 biosynthesis I
autoinducer AI-2 biosynthesis II (Vibrio)
L-methionine degradation I (to L-homocysteine)
S-adenosyl-L-methionine cycle I
S-adenosyl-L-methionine cycle II
S-adenosyl-L-methionine + a demethylated methyl donor → S-adenosyl-L-homocysteine + a methylated methyl donor + H+
caffeine degradation I (main, plants)
3-methylxanthine + a demethylated methyl donor → xanthine + a methylated methyl donor
theophylline + a demethylated methyl donor → 3-methylxanthine + a methylated methyl donor
caffeine + a demethylated methyl donor → theophylline + a methylated methyl donor
In Reactions of unknown directionality:
Not in pathways:
cycloartenol + a demethylated methyl donor = 4α,14α-dimethyl-9β,19-cyclo-5α-cholest-24-en-3β-ol + a methylated methyl donor
4α-methyl-5α-cholesta-7,24-dien-3β-ol + a demethylated methyl donor = 5α-cholesta-7,24-dien-3β-ol + a methylated methyl donor
24-methylenecycloartanol + a demethylated methyl donor = cycloeucalenol + a methylated methyl donor
24-methylenelophenol + a demethylated methyl donor = episterol + a methylated methyl donor
24-ethylidenelophenol + a demethylated methyl donor = avenasterol + a methylated methyl donor
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