Accepted name: thiol S-methyltransferase
Reaction: S-adenosyl-L-methionine + a thiol = S-adenosyl-L-homocysteine + a methyl thioether
Other name(s): S-methyltransferase; thiol methyltransferase; TMT
Systematic name: S-adenosyl-L-methionine:thiol S-methyltransferase
Comments: H2S and a variety of alkyl, aryl and heterocyclic thiols and hydroxy thiols can act as acceptors.
1.  Borchardt, R.T. and Cheng, C.F. Purification and characterization of rat liver microsomal thiol methyltransferase. Biochim. Biophys. Acta 522 (1978) 340–353. [PMID: 623768]
2.  Bremer, J. and Greenberg, D.M. Enzymic methylation of foreign sulfhydryl compounds. Biochim. Biophys. Acta 46 (1961) 217–224.
3.  Weisiger, R.A. and Jakoby, W.B. Thiol S-methyltransferase from rat liver. Arch. Biochem. Biophys. 196 (1979) 631–637. [PMID: 485170]
[EC created 1965]
Accepted name: methanol—corrinoid protein Co-methyltransferase
Reaction: methanol + a [Co(I) methanol-specific corrinoid protein] = a [methyl-Co(III) methanol-specific corrinoid protein] + H2O
Other name(s): methanol cobalamin methyltransferase; methanol:5-hydroxybenzimidazolylcobamide methyltransferase; MT 1 (ambiguous); methanol—5-hydroxybenzimidazolylcobamide Co-methyltransferase; mtaB (gene name)
Systematic name: methanol:5-hydroxybenzimidazolylcobamide Co-methyltransferase
Comments: The enzyme, which catalyses the transfer of methyl groups from methanol to a methanol-specific corrinoid protein (MtaC), is involved in methanogenesis from methanol. Methylation of the corrinoid protein requires the central cobalt to be in the Co(I) state. During methylation the cobalt is oxidized to the Co(III) state. Free cob(I)alamin can substitute for the corrinoid protein in vitro [2]. Inactivated by oxygen and other oxidizing agents, and reactivated by catalytic amounts of ATP and hydrogen.
1.  van der Meijden, P., te Brömmelstroet, B.W., Poirot, C.M., van der Drift, C. and Vogels, G.D. Purification and properties of methanol:5-hydroxybenzimidazolylcobamide methyltransferase from Methanosarcina barkeri. J. Bacteriol. 160 (1984) 629–635. [PMID: 6438059]
2.  Sauer, K. and Thauer, R.K. Methanol:coenzyme M methyltransferase from Methanosarcina barkeri – substitution of the corrinoid harbouring subunit MtaC by free cob(I)alamin. Eur. J. Biochem. 261 (1999) 674–681. [PMID: 10215883]
[EC created 1989, modified 2012]
Accepted name: isobutyraldoxime O-methyltransferase
Reaction: S-adenosyl-L-methionine + 2-methylpropanal oxime = S-adenosyl-L-homocysteine + 2-methylpropanal O-methyloxime
Other name(s): aldoxime methyltransferase; S-adenosylmethionine:aldoxime O-methyltransferase; aldoxime O-methyltransferase
Systematic name: S-adenosyl-L-methionine:2-methylpropanal-oxime O-methyltransferase
Comments: Oximes of C4 to C6 aldehydes can act as acceptors; the most active substrate is 2-methylbutyroaldoxime.
1.  Harper, D.B. and Kennedy, J.T. Purification and properties of S-adenosylmethionine: aldoxime O-methyltransferase from Pseudomonas sp. N.C.I.B. 11652. Biochem. J. 226 (1985) 147–153. [PMID: 3977861]
[EC created 1989]
Deleted entry: bergaptol O-methyltransferase. Now included with EC, 5-hydroxyfuranocoumarin 5-O-methyltransferase. The reaction with bergaptol is a specific example of the general reaction associated with EC
[EC created 1989, deleted 2006]
Deleted entry: xanthotoxol O-methyltransferase. Enzyme is identical to EC, 8-hydroxyfuranocoumarin 8-O-methyltransferase
[EC created 1989, deleted 2008]
Accepted name: tabersonine 16-O-methyltransferase
Reaction: S-adenosyl-L-methionine + 16-hydroxytabersonine = S-adenosyl-L-homocysteine + 16-methoxytabersonine
Other name(s): 11-demethyl-17-deacetylvindoline 11-methyltransferase; 11-O-demethyl-17-O-deacetylvindoline O-methyltransferase; S-adenosyl-L-methionine:11-O-demethyl-17-O-deacetylvindoline 11-O-methyltransferase
Systematic name: S-adenosyl-L-methionine:16-hydroxytabersonine 16-O-methyltransferase
Comments: Involved in the biosynthesis of vindoline from tabersonine in the Madagascar periwinkle, Catharanthus roseus.
1.  De Luca, V., Balsevich, J., Tyler, R.T., Eilert, U., Panchuk, B.D. and Kurz, W.G.W. Biosynthesis of indole alkaloids - developmental regulation of the biosynthetic-pathway from tabersonine to vindoline in Catharanthus roseus. J. Plant Physiol. 125 (1986) 147–156.
2.  Fahn, W., Laussermair, E., Deus-Neumann, B. and Stöckigt, J. Late enzymes of vindoline biosynthesis. S-Adenosyl-L-methionine:11-O-demethyl-17-O-deacetylvindoline 11-O-methylase and unspecific acetylesterase. Plant Cell Rep. 4 (1985) 337–340. [PMID: 24254077]
[EC created 1989, modified 2005]
Accepted name: tocopherol O-methyltransferase
Reaction: (1) S-adenosyl-L-methionine + γ-tocopherol = S-adenosyl-L-homocysteine + α-tocopherol
(2) S-adenosyl-L-methionine + δ-tocopherol = S-adenosyl-L-homocysteine + β-tocopherol
(3) S-adenosyl-L-methionine + γ-tocotrienol = S-adenosyl-L-homocysteine + α-tocotrienol
(4) S-adenosyl-L-methionine + δ-tocotrienol = S-adenosyl-L-homocysteine + β-tocotrienol
Other name(s): γ-tocopherol methyltransferase; VTE4 (gene name)
Systematic name: S-adenosyl-L-methionine:γ-tocopherol 5-O-methyltransferase
Comments: The enzymes from plants and photosynthetic bacteria have similar efficiency with the γ and δ isomers of tocopherols and tocotrienols.
1.  Camara, B. and D'Harlingue, A. Demonstration and solubilization of S-adenosylmethionine - γ-tocopherol methyltransferase from capsicum chromoplasts. Plant Cell Rep. 4 (1985) 31–32. [PMID: 24253640]
2.  Koch, M., Lemke, R., Heise, K.P. and Mock, H.P. Characterization of γ-tocopherol methyltransferases from Capsicum annuum L and Arabidopsis thaliana. Eur. J. Biochem. 270 (2003) 84–92. [PMID: 12492478]
3.  Zhang, G.Y., Liu, R.R., Xu, G., Zhang, P., Li, Y., Tang, K.X., Liang, G.H. and Liu, Q.Q. Increased α-tocotrienol content in seeds of transgenic rice overexpressing Arabidopsis γ-tocopherol methyltransferase. Transgenic Res. 22 (2013) 89–99. [PMID: 22763462]
[EC created 1989, modified 2013]
Accepted name: thioether S-methyltransferase
Reaction: S-adenosyl-L-methionine + dimethyl sulfide = S-adenosyl-L-homocysteine + trimethylsulfonium
Other name(s): S-adenosyl-L-methionine:thioether S-methyltransferase; thioether methyltransferase
Systematic name: S-adenosyl-L-methionine:dimethyl-sulfide S-methyltransferase
Comments: Also acts on dimethyl selenide, dimethyl telluride, diethyl sulfide, 1,4-dithiane and many other thioethers.
1.  Mozier, N.M., McConnell, P. and Hoffman, J.L. S-Adenosyl-L-methionine:thioether S-methyltransferase, a new enzyme in sulfur and selenium metabolism. J. Biol. Chem. 263 (1988) 4527–4531. [PMID: 3350800]
[EC created 1990]
Accepted name: 3-hydroxyanthranilate 4-C-methyltransferase
Reaction: S-adenosyl-L-methionine + 3-hydroxyanthranilate = S-adenosyl-L-homocysteine + 3-hydroxy-4-methylanthranilate
Other name(s): 3-hydroxyanthranilate 4-methyltransferase
Systematic name: S-adenosyl-L-methionine:3-hydroxyanthranilate 4-C-methyltransferase
Comments: Involved in the biosynthesis of the antibiotic actinomycin in Streptomyces antibioticus.
1.  Fawaz, F. and Jones, G.H. Actinomycin synthesis in Streptomyces antibioticus. Purification and properties of a 3-hydroxyanthranilate 4-methyltransferase. J. Biol. Chem. 263 (1988) 4602–4606. [PMID: 2450873]
[EC created 1990]
Accepted name: diphthine synthase
Reaction: 3 S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-aminopropyl]-L-histidine-[translation elongation factor 2] = 3 S-adenosyl-L-homocysteine + diphthine-[translation elongation factor 2] (overall reaction)
(1a) S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-aminopropyl]-L-histidine-[translation elongation factor 2] = S-adenosyl-L-homocysteine + 2-[(3S)-3-carboxy-3-(methylamino)propyl]-L-histidine-[translation elongation factor 2]
(1b) S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-(methylamino)propyl]-L-histidine-[translation elongation factor 2] = S-adenosyl-L-homocysteine + 2-[(3S)-3-carboxy-3-(dimethylamino)propyl]-L-histidine-[translation elongation factor 2]
(1c) S-adenosyl-L-methionine + 2-[(3S)-3-carboxy-3-(dimethylamino)propyl]-L-histidine-[translation elongation factor 2] = S-adenosyl-L-homocysteine + diphthine-[translation elongation factor 2]
Glossary: diphthine = 2-[(3S)-3-carboxy-3-(trimethylamino)propyl]-L-histidine
Other name(s): S-adenosyl-L-methionine:elongation factor 2 methyltransferase (ambiguous); diphthine methyltransferase (ambiguous); S-adenosyl-L-methionine:2-(3-carboxy-3-aminopropyl)-L-histidine-[translation elongation factor 2] methyltransferase; Dph5 (ambiguous)
Systematic name: S-adenosyl-L-methionine:2-[(3S)-3-carboxy-3-aminopropyl]-L-histidine-[translation elongation factor 2] methyltransferase (diphthine-[translation elongation factor 2]-forming)
Comments: This archaeal enzyme produces the trimethylated product diphthine, which is converted into diphthamide by EC, diphthine—ammonia ligase. Different from the eukaryotic enzyme, which produces diphthine methyl ester (cf. EC In the archaeon Pyrococcus horikoshii the enzyme acts on His600 of elongation factor 2.
1.  Zhu, X., Kim, J., Su, X. and Lin, H. Reconstitution of diphthine synthase activity in vitro. Biochemistry 49 (2010) 9649–9657. [PMID: 20873788]
[EC created 1990, modified 2013, modified 2015]
Accepted name: 3-hydroxy-16-methoxy-2,3-dihydrotabersonine N-methyltransferase
Reaction: S-adenosyl-L-methionine + 3-hydroxy-16-methoxy-2,3-dihydrotabersonine = S-adenosyl-L-homocysteine + deacetoxyvindoline
Other name(s): 16-methoxy-2,3-dihydro-3-hydroxytabersonine methyltransferase; NMT; 16-methoxy-2,3-dihydro-3-hydroxytabersonine N-methyltransferase; S-adenosyl-L-methionine:16-methoxy-2,3-dihydro-3-hydroxytabersonine N-methyltransferase
Systematic name: S-adenosyl-L-methionine:3-hydroxy-16-methoxy-2,3-dihydrotabersonine N-methyltransferase
Comments: Involved in the biosynthesis of vindoline from tabersonine in the Madagascar periwinkle Catharanthus roseus.
1.  De Luca, V., Balsevich, J., Tyler, R.T., Eilert, U., Panchuk, B.D. and Kurz, W.G.W. Biosynthesis of indole alkaloids - developmental regulation of the biosynthetic-pathway from tabersonine to vindoline in Catharanthus roseus. J. Plant Physiol. 125 (1986) 147–156.
2.  De Luca, V. and Cutler, A.J. Subcellular localization of enzymes involved in indole alkaloid biosynthesis in Catharanthus roseus. Plant Physiol. 85 (1987) 1099–1102. [PMID: 16665811]
[EC created 1990, modified 2005]

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