The Enzyme Database

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EC 1.1.1.219     
Accepted name: dihydroflavonol 4-reductase
Reaction: a (2R,3S,4S)-leucoanthocyanidin + NADP+ = a (2R,3R)-dihydroflavonol + NADPH + H+
For diagram of flavonoid biosynthesis, click here
Other name(s): dihydrokaempferol 4-reductase; dihydromyricetin reductase; NADPH-dihydromyricetin reductase; dihydroquercetin reductase; DFR (gene name); cis-3,4-leucopelargonidin:NADP+ 4-oxidoreductase; dihydroflavanol 4-reductase (incorrect)
Systematic name: (2R,3S,4S)-leucoanthocyanidin:NADP+ 4-oxidoreductase
Comments: This plant enzyme, involved in the biosynthesis of anthocyanidins, is known to act on (+)-dihydrokaempferol, (+)-taxifolin, and (+)-dihydromyricetin, although some enzymes may act only on a subset of these compounds. Each dihydroflavonol is reduced to the corresponding cis-flavan-3,4-diol. NAD+ can act instead of NADP+, but more slowly.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 83682-99-9
References:
1.  Heller, W., Forkmann, G., Britsch, L. and Grisebach, H. Enzymatic reduction of (+)-dihydroflavonols to flavan-3,4-cis- diols with flower extracts from Matthiola incana and its role in anthocyanin biosynthesis. Planta 165 (1985) 284–287. [PMID: 24241054]
2.  Stafford, H.A. and Lester, H.H. Flavan-3-ol biosynthesis the conversion of (+)-dihydromyricetin to its flavan-3,4-diol (leucodelphinidin) and to (+)-gallocatechin by reductases extracted from tissue-cultures of Ginkgo biloba and Pseudotsuga-menziesii. Plant Physiol. 78 (1985) 791–794. [PMID: 16664326]
3.  Fischer, D., Stich, K., Britsch, L. and Grisebach, H. Purification and characterization of (+)dihydroflavonol (3-hydroxyflavanone) 4-reductase from flowers of Dahlia variabilis. Arch. Biochem. Biophys. 264 (1988) 40–47. [DOI] [PMID: 3293532]
4.  Li, H., Qiu, J., Chen, F., Lv, X., Fu, C., Zhao, D., Hua, X. and Zhao, Q. Molecular characterization and expression analysis of dihydroflavonol 4-reductase (DFR) gene in Saussurea medusa. Mol. Biol. Rep. 39 (2012) 2991–2999. [DOI] [PMID: 21701830]
[EC 1.1.1.219 created 1989, modified 2016]
 
 
EC 1.14.11.23      
Transferred entry: flavonol synthase. Now EC 1.14.20.6, flavonol synthase
[EC 1.14.11.23 created 2004, deleted 2018]
 
 
EC 1.14.13.88      
Transferred entry: flavanoid 3,5-hydroxylase. Now EC 1.14.14.81, flavanoid 3,5-hydroxylase
[EC 1.14.13.88 created 2004, deleted 2018]
 
 
EC 1.14.14.81     
Accepted name: flavanoid 3′,5′-hydroxylase
Reaction: a flavanone + 2 [reduced NADPH—hemoprotein reductase] + 2 O2 = a 3′,5′-dihydroxyflavanone + 2 [oxidized NADPH—hemoprotein reductase] + 2 H2O (overall reaction)
(1a) a flavanone + [reduced NADPH—hemoprotein reductase] + O2 = a 3′-hydroxyflavanone + [oxidized NADPH—hemoprotein reductase] + H2O
(1b) a 3′-hydroxyflavanone + [reduced NADPH—hemoprotein reductase] + O2 = a 3′,5′-dihydroxyflavanone + [oxidized NADPH—hemoprotein reductase] + H2O
For diagram of myricetin biosynthesis, click here, for diagram of the biosynthesis of naringenin derivatives, click here and for diagram of flavonoid biosynthesis, click here
Other name(s): flavonoid 3′,5′-hydroxylase
Systematic name: flavanone,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (3′,5′-dihydroxylating)
Comments: A cytochrome P-450 (heme-thiolate) protein found in plants. The 3′,5′-dihydroxyflavanone is formed via the 3′-hydroxyflavanone. In Petunia hybrida the enzyme acts on naringenin, eriodictyol, dihydroquercetin (taxifolin) and dihydrokaempferol (aromadendrin). The enzyme catalyses the hydroxylation of 5,7,4′-trihydroxyflavanone (naringenin) at either the 3′ position to form eriodictyol or at both the 3′ and 5′ positions to form 5,7,3′,4′,5′-pentahydroxyflavanone (dihydrotricetin). The enzyme also catalyses the hydroxylation of 3,5,7,3′,4′-pentahydroxyflavanone (taxifolin) at the 5′ position, forming ampelopsin.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 94047-23-1
References:
1.  Menting, J., Scopes, R.K. and Stevenson, T.W. Characterization of flavonoid 3′,5′-hydroxylase in microsomal membrane fraction of Petunia hybrida flowers. Plant Physiol. 106 (1994) 633–642. [PMID: 12232356]
2.  Shimada, Y., Nakano-Shimada, R., Ohbayashi, M., Okinaka, Y., Kiyokawa, S. and Kikuchi, Y. Expression of chimeric P450 genes encoding flavonoid-3′, 5′-hydroxylase in transgenic tobacco and petunia plants1. FEBS Lett. 461 (1999) 241–245. [DOI] [PMID: 10567704]
3.  de Vetten, N., ter Horst, J., van Schaik, H.P., de Boer, A., Mol, J. and Koes, R. A cytochrome b5 is required for full activity of flavonoid 3′, 5′-hydroxylase, a cytochrome P450 involved in the formation of blue flower colors. Proc. Natl. Acad. Sci. USA 96 (1999) 778–783. [DOI] [PMID: 9892710]
[EC 1.14.14.81 created 2004 as EC 1.14.13.88, transferred 2018 to EC 1.14.14.81]
 
 
EC 1.14.20.6     
Accepted name: flavonol synthase
Reaction: a dihydroflavonol + 2-oxoglutarate + O2 = a flavonol + succinate + CO2 + H2O
For diagram of flavonoid biosynthesis, click here, for diagram of kaempferol biosynthesis, click here and for diagram of myricetin biosynthesis, click here
Other name(s): FLS (gene name)
Systematic name: dihydroflavonol,2-oxoglutarate:oxygen oxidoreductase
Comments: In addition to the desaturation of (2R,3R)-dihydroflavonols to flavonols, the enzyme from Citrus unshiu (satsuma mandarin) also has a non-specific activity that trans-hydroxylates the flavanones (2S)-naringenin and the unnatural (2R)-naringenin at C-3 to kaempferol and (2R,3R)-dihydrokaempferol, respectively [2]. Requires Fe2+.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 146359-76-4
References:
1.  Wellmann, F., Lukačin, R., Moriguchi, T., Britsch, L., Schiltz, E. and Matern, U. Functional expression and mutational analysis of flavonol synthase from Citrus unshiu. Eur. J. Biochem. 269 (2002) 4134–4142. [DOI] [PMID: 12180990]
2.  Lukačin, R., Wellmann, F., Britsch, L., Martens, S. and Matern, U. Flavonol synthase from Citrus unshiu is a bifunctional dioxygenase. Phytochemistry 62 (2003) 287–292. [DOI] [PMID: 12620339]
3.  Martens, S., Forkmann, G., Britsch, L., Wellmann, F., Matern, U. and Lukačin, R. Divergent evolution of flavonoid 2-oxoglutarate-dependent dioxygenases in parsley. FEBS Lett. 544 (2003) 93–98. [DOI] [PMID: 12782296]
4.  Turnbull, J.J., Nakajima, J., Welford, R.W., Yamazaki, M., Saito, K. and Schofield, C.J. Mechanistic studies on three 2-oxoglutarate-dependent oxygenases of flavonoid biosynthesis: anthocyanidin synthase, flavonol synthase, and flavanone 3β-hydroxylase. J. Biol. Chem. 279 (2004) 1206–1216. [DOI] [PMID: 14570878]
[EC 1.14.20.6 created 2004 as EC 1.14.11.23, transferred 2018 to EC 1.14.20.6]
 
 
EC 2.1.1.149      
Deleted entry: myricetin O-methyltransferase. Now covered by EC 2.1.1.267, flavonoid 3′,5′-methyltransferase.
[EC 2.1.1.149 created 2003, modified 2011, deleted 2013]
 
 
EC 2.1.1.267     
Accepted name: flavonoid 3′,5′-methyltransferase
Reaction: (1) S-adenosyl-L-methionine + a 3′-hydroxyflavonoid = S-adenosyl-L-homocysteine + a 3′-methoxyflavonoid
(2) S-adenosyl-L-methionine + a 5′-hydroxy-3′-methoxyflavonoid = S-adenosyl-L-homocysteine + a 3′,5′-dimethoxyflavonoid
For diagram of anthocyanidin glucoside biosynthesis, click here
Glossary: delphinidin = 3,3′,4′,5,5′,7-hexahydroxyflavylium
cyanidin = 3,3′,4′,5,7-pentahydroxyflavylium
myricetin = 3,3′,4′,5,5′,7-hexahydroxyflavone
quercetin = 3,3′,4′,5,7-pentahydroxyflavone
Other name(s): AOMT; CrOMT2
Systematic name: S-adenosyl-L-methionine:flavonoid 3′-O-methyltransferase
Comments: Isolated from Vitis vinifera (grape) [2]. Most active with delphinidin 3-glucoside but also acts on cyanidin 3-glucoside, cyanidin, myricetin, quercetin and quercetin 3-glucoside. The enzyme from Catharanthus roseus was most active with myricetin [1].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Cacace, S., Schröder, G., Wehinger, E., Strack, D., Schmidt, J. and Schröder, J. A flavonol O-methyltransferase from Catharanthus roseus performing two sequential methylations. Phytochemistry 62 (2003) 127–137. [DOI] [PMID: 12482447]
2.  Hugueney, P., Provenzano, S., Verries, C., Ferrandino, A., Meudec, E., Batelli, G., Merdinoglu, D., Cheynier, V., Schubert, A. and Ageorges, A. A novel cation-dependent O-methyltransferase involved in anthocyanin methylation in grapevine. Plant Physiol. 150 (2009) 2057–2070. [DOI] [PMID: 19525322]
[EC 2.1.1.267 created 2013, modified 2014]
 
 
EC 2.4.1.234     
Accepted name: kaempferol 3-O-galactosyltransferase
Reaction: UDP-α-D-galactose + kaempferol = UDP + kaempferol 3-O-β-D-galactoside
For diagram of kaempferol biosynthesis, click here
Other name(s): F3GalTase; UDP-galactose:kaempferol 3-O-β-D-galactosyltransferase
Systematic name: UDP-α-D-galactose:kaempferol 3-O-β-D-galactosyltransferase
Comments: Acts on the endogenous flavonols kaempferol and quercetin, to a lesser extent on myricetin and fisetin, and weakly on galangin and isorhamnetin. The reaction can occur equally well in both directions.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Miller, K.D., Guyon, V., Evans, J.N., Shuttleworth, W.A. and Taylor, L.P. Purification, cloning, and heterologous expression of a catalytically efficient flavonol 3-O-galactosyltransferase expressed in the male gametophyte of Petunia hybrida. J. Biol. Chem. 274 (1999) 34011–34019. [DOI] [PMID: 10567367]
[EC 2.4.1.234 created 2004]
 
 
EC 2.4.1.237     
Accepted name: flavonol 7-O-β-glucosyltransferase
Reaction: UDP-glucose + a flavonol = UDP + a flavonol 7-O-β-D-glucoside
For diagram of quercetin 7-O-Glycoside biosynthesis, click here
Other name(s): UDP-glucose:flavonol 7-O-glucosyltransferase
Systematic name: UDP-glucose:flavonol 7-O-β-D-glucosyltransferase
Comments: Acts on the flavonols gossypetin (8-hydroxyquercetin) and to a lesser extent on quercetin, kaempferol and myricetin.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 83682-90-0
References:
1.  Stich, K., Halbwirth, H., Wurst, F. and Forkmann, G. UDP-glucose: flavonol 7-O-glucosyltransferase activity in flower extracts of Chrysanthemum segetum. Z. Naturforsch. C 52 (1997) 153–158. [PMID: 9167271]
[EC 2.4.1.237 created 2004]
 
 
EC 2.4.2.56     
Accepted name: kaempferol 3-O-xylosyltransferase
Reaction: UDP-α-D-xylose + kaempferol = UDP + kaempferol 3-O-β-D-xyloside
For diagram of kaempferol biosynthesis, click here
Other name(s): F3XT; UDP-D-xylose:flavonol 3-O-xylosyltransferase; flavonol 3-O-xylosyltransferase
Systematic name: UDP-α-D-xylose:kaempferol 3-O-D-xylosyltransferase
Comments: The enzyme from the plant Euonymus alatus also catalyses the 3-O-D-xylosylation of other flavonols (e.g. quercetin, isorhamnetin, rhamnetin, myricetin, fisetin) with lower activity.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Ishikura, N. and Yang, Z.Q. UDP-D-xylose: flavonol 3-O-xylosyltransferase from young leaves of Euonymus alatus f. ciliato-dentatus. Z. Naturforsch. C: Biosci. 46 (1991) 1003–1010.
[EC 2.4.2.56 created 2013]
 
 


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