The Enzyme Database

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EC 1.14.19.59     
Accepted name: tryptophan 6-halogenase
Reaction: (1) L-tryptophan + FADH2 + chloride + O2 + H+ = 6-chloro-L-tryptophan + FAD + 2 H2O
(2) D-tryptophan + FADH2 + chloride + O2 + H+ = 6-chloro-D-tryptophan + FAD + 2 H2O
For diagram of chlorotryptophan biosynthesis, click here
Other name(s): sttH (gene name); thdH (gene name)
Systematic name: L-tryptophan:FADH2 oxidoreductase (6-halogenating)
Comments: The enzyme is a flavin-dependent halogenase that has been described from several bacterial species. It utilizes molecular oxygen to oxidize the FADH2 cofactor, giving C4a-hydroperoxyflavin, which then reacts with chloride to produce a hypochlorite ion. The latter reacts with an active site lysine to generate a chloramine, which chlorinates the substrate. cf. EC 1.14.19.58, tryptophan 5-halogenase, and EC 1.14.19.9, tryptophan 7-halogenase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Zeng, J. and Zhan, J. Characterization of a tryptophan 6-halogenase from Streptomyces toxytricini. Biotechnol. Lett. 33 (2011) 1607–1613. [DOI] [PMID: 21424165]
2.  Milbredt, D., Patallo, E.P. and van Pee, K.H. A tryptophan 6-halogenase and an amidotransferase are involved in thienodolin biosynthesis. ChemBioChem 15 (2014) 1011–1020. [DOI] [PMID: 24692213]
3.  Shepherd, S.A., Menon, B.R., Fisk, H., Struck, A.W., Levy, C., Leys, D. and Micklefield, J. A structure-guided switch in the regioselectivity of a tryptophan halogenase. ChemBioChem 17 (2016) 821–824. [DOI] [PMID: 26840773]
[EC 1.14.19.59 created 2018]
 
 
EC 1.14.19.76     
Accepted name: flavone synthase II
Reaction: a flavanone + [reduced NADPH—hemoprotein reductase] + O2 = a flavone + [oxidized NADPH—hemoprotein reductase] + 2 H2O
Other name(s): CYP93B16 (gene name); CYP93G1 (gene name); FNS II
Systematic name: flavanone,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (flavone-forming)
Comments: A cytochrome P-450 (heme-thiolate) protein found in plants. The rice enzyme channels flavanones to the biosynthesis of tricin O-linked conjugates. cf. EC 1.14.20.5, flavone synthase I.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Martens, S. and Forkmann, G. Cloning and expression of flavone synthase II from Gerbera hybrids. Plant J. 20 (1999) 611–618. [PMID: 10652133]
2.  Fliegmann, J., Furtwangler, K., Malterer, G., Cantarello, C., Schuler, G., Ebel, J. and Mithofer, A. Flavone synthase II (CYP93B16) from soybean (Glycine max L.). Phytochemistry 71 (2010) 508–514. [PMID: 20132953]
3.  Lam, P.Y., Zhu, F.Y., Chan, W.L., Liu, H. and Lo, C. Cytochrome P450 93G1 is a flavone synthase II that channels flavanones to the biosynthesis of tricin O-linked conjugates in rice. Plant Physiol. 165 (2014) 1315–1327. [PMID: 24843076]
[EC 1.14.19.76 created 2018]
 
 
EC 1.14.99.47     
Accepted name: (+)-larreatricin hydroxylase
Reaction: (+)-larreatricin + reduced acceptor + O2 = (+)-3′-hydroxylarreatricin + acceptor + H2O
Glossary: (+)-larreatricin = 4,4′-[(2R,3R,4S,5R)-3,4-dimethyltetrahydrofuran-2,5-diyl]bisphenol
Systematic name: (+)-larreatricin:oxygen 3′-hydroxylase
Comments: Isolated from the plant Larrea tridentata (creosote bush). The enzyme has a strong preference for the 3′ position of (+)-larreatricin.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Cho, M.H., Moinuddin, S.G., Helms, G.L., Hishiyama, S., Eichinger, D., Davin, L.B. and Lewis, N.G. (+)-Larreatricin hydroxylase, an enantio-specific polyphenol oxidase from the creosote bush (Larrea tridentata). Proc. Natl. Acad. Sci. USA 100 (2003) 10641–10646. [DOI] [PMID: 12960376]
[EC 1.14.99.47 created 2012]
 
 
EC 2.1.1.175     
Accepted name: tricin synthase
Reaction: 2 S-adenosyl-L-methionine + tricetin = 2 S-adenosyl-L-homocysteine + 3′,5′-O-dimethyltricetin (overall reaction)
(1a) S-adenosyl-L-methionine + tricetin = S-adenosyl-L-homocysteine + 3′-O-methyltricetin
(1b) S-adenosyl-L-methionine + 3′-O-methyltricetin = S-adenosyl-L-homocysteine + 3′,5′-O-dimethyltricetin
Glossary: tricin = 3′,5′-O-dimethyltricetin
Other name(s): ROMT-17; ROMT-15; HvOMT1; ZmOMT1
Systematic name: S-adenosyl-L-methionine:tricetin 3′,5′-O-dimethyltransferase
Comments: The enzymes from Oryza sativa (ROMT-15 and ROMT-17) catalyses the stepwise methylation of tricetin to its 3′-mono- and 3′,5′-dimethyl ethers. In contrast with the wheat enzyme (EC 2.1.1.169, tricetin 3′,4′,5′-O-trimethyltransferase), tricetin dimethyl ether is not converted to its 3′,4′,5′-trimethylated ether derivative [1]. The enzymes from Hordeum vulgare (HvOMT1) and from Zea mays (ZmOMT1) form the 3′,5′-dimethyl derivative as the major product [2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Lee, Y.J., Kim, B.G., Chong, Y., Lim, Y. and Ahn, J.H. Cation dependent O-methyltransferases from rice. Planta 227 (2008) 641–647. [DOI] [PMID: 17943312]
2.  Zhou, J.-M., Fukushi, Y., Wollenweber, E., Ibrahim, R.K. Characterization of two O-methyltransferase-like genes in barley and maize. Pharm. Biol. 46 (2008) 26–34.
[EC 2.1.1.175 created 2010]
 
 
EC 2.1.1.390     
Accepted name: gentamicin X2 methyltransferase
Reaction: gentamicin X2 + 2 S-adenosyl-L-methionine + reduced acceptor = geneticin + 5′-deoxyadenosine + L-methionine + S-adenosyl-L-homocysteine + oxidized acceptor (overall reaction)
(1a) S-adenosyl-L-methionine + cob(I)alamin = S-adenosyl-L-homocysteine + methylcob(III)alamin
(1b) methylcob(III)alamin + gentamicin X2 + S-adenosyl-L-methionine = cob(III)alamin + geneticin + 5′-deoxyadenosine + L-methionine
(1c) cob(III)alamin + reduced acceptor = cob(I)alamin + oxidized acceptor
Glossary: geneticin = G418 = (1R,2S,3S,4R,6S)-4,6-diamino-3-{[3-deoxy-4-C-methyl-3-(methylamino)-β-L-arabinopyranosyl]oxy}-2-hydroxycyclohexyl 2-amino-2,7-dideoxy-D-glycero-α-D-gluco-heptopyranoside
Other name(s): genK (gene name); gntK (gene name); gentamicin C-methyltransferase (ambiguous)
Systematic name: S-adenosyl-L-methionine:gentamicin X2 C6′-methyltransferase
Comments: The enzyme, isolated from the bacterium Micromonospora echinospora, has a single [4Fe-4S] cluster per monomer. It is a radical S-adenosyl-L-methionine (SAM) enzyme with a methylcob(III)alamin cofactor. The enzyme uses two molecues of SAM for the reaction. One molecule forms a 5′-deoxyadenosyl radical, while the other is used to methylate the cobalamin cofactor. It catalyses methylation of the 6′-carbon of gentamicin X2 (GenX2) to produce genetricin (G418) during the biosynthesis of gentamicins. The 6′-pro-R-hydrogen atom of GenX2 is stereoselectively abstracted by the 5′-deoxyadenosyl radical and methylation occurs with retention of configuration at C6′. The regeneration of cob(I)alamin from cob(III)alamin is carried out with an as yet unidentified electron donor.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Kim, J.Y., Suh, J.W., Kang, S.H., Phan, T.H., Park, S.H. and Kwon, H.J. Gene inactivation study of gntE reveals its role in the first step of pseudotrisaccharide modifications in gentamicin biosynthesis. Biochem. Biophys. Res. Commun. 372 (2008) 730–734. [DOI] [PMID: 18533111]
2.  Hong, W. and Yan, L. Identification of gntK, a gene required for the methylation of purpurosamine C-6′ in gentamicin biosynthesis. J. Gen. Appl. Microbiol. 58 (2012) 349–356. [DOI] [PMID: 23149679]
3.  Kim, H.J., McCarty, R.M., Ogasawara, Y., Liu, Y.N., Mansoorabadi, S.O., LeVieux, J. and Liu, H.W. GenK-catalyzed C-6′ methylation in the biosynthesis of gentamicin: isolation and characterization of a cobalamin-dependent radical SAM enzyme. J. Am. Chem. Soc. 135 (2013) 8093–8096. [DOI] [PMID: 23679096]
4.  Kim, H.J., Liu, Y.N., McCarty, R.M. and Liu, H.W. Reaction Catalyzed by GenK, a Cobalamin-Dependent Radical S-Adenosyl-l-methionine Methyltransferase in the Biosynthetic Pathway of Gentamicin, Proceeds with Retention of Configuration. J. Am. Chem. Soc. 139 (2017) 16084–16087. [DOI] [PMID: 29091410]
[EC 2.1.1.390 created 2023]
 
 


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