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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]

1.14.11.19

Transferred entry:

anthocyanidin synthase. Now EC 1.14.20.4, anthocyanidin synthase

[EC 1.14.11.19 created 2001, modified 2017, deleted 2018]

1.14.13.19

Accepted name:

taxifolin 8-monooxygenase

Reaction:

taxifolin + NAD(P)H + H⁺ + O₂ = 2,3-dihydrogossypetin + NAD(P)⁺ + H₂O

Other name(s):

taxifolin hydroxylase

Systematic name:

taxifolin,NAD(P)H:oxygen oxidoreductase (8-hydroxylating)

Comments:

A flavoprotein, converting a flavanol into a flavanone. Also acts on fustin, but not on catechin, quercetin or mollisacidin.

Links to other databases:

BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 39307-19-2

References:

1.	Jeffrey, A.M., Knight, M. and Evans, W.C. The bacterial degradation of flavonoids. Hydroxylation of the A-ring of taxifolin by a soil pseudomonad. Biochem. J. 130 (1972) 373–381. [PMID: 4146277]

[EC 1.14.13.19 created 1976]

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]

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]

1.14.20.4

Accepted name:

anthocyanidin synthase

Reaction:

a (2R,3S,4S)-leucoanthocyanidin + 2-oxoglutarate + O₂ = an anthocyanidin + succinate + CO₂ + 2 H₂O (overall reaction)
(1a) a (2R,3S,4S)-leucoanthocyanidin + 2-oxoglutarate + O₂ = a (4S)- 2,3-dehydroflavan-3,4-diol + succinate + CO₂ + H₂O
(1b) a (4S)- 2,3-dehydroflavan-3,4-diol = an anthocyanidin + H₂O

For diagram of anthocyanin biosynthesis, click here

Glossary:

taxifolin = 3,4-dihydroquercitin

Other name(s):

leucocyanidin oxygenase; leucocyanidin,2-oxoglutarate:oxygen oxidoreductase; ANS (gene name)

Systematic name:

(2R,3S,4S)-leucoanthocyanidin,2-oxoglutarate:oxygen oxidoreductase

Comments:

The enzyme requires iron(II) and ascorbate. It is involved in the pathway by which many flowering plants make anthocyanin flower pigments (glycosylated anthocyandins). The enzyme hydroxylates the C-3 carbon, followed by a trans diaxial elimination, forming a C-2,C-3 enol. The product loses a second water molecule to form anthocyanidins. When assayed in vitro, non-enzymic epimerization of the product can lead to formation of dihydroflavanols. Thus when the substrate is leucocyanidin, a mixture of (+)-taxifolin and (+)-epitaxifolin are formed. The enzyme can also oxidize the formed (+)-taxifolin to quercetin (cf. EC 1.14.20.6, flavonol synthase) [2,3].

Links to other databases:

BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 180984-01-4

References:

1.	Saito, K., Kobayashi, M., Gong, Z., Tanaka, Y. and Yamazaki, M. Direct evidence for anthocyanidin synthase as a 2-oxoglutarate-dependent oxygenase: molecular cloning and functional expression of cDNA from a red forma of Perilla frutescens. Plant J. 17 (1999) 181–190. [DOI] [PMID: 10074715]
2.	Turnbull, J.J., Sobey, W.J., Aplin, R.T., Hassan, A., Firmin, J.L., Schofield, C.J. and Prescott, A.G. Are anthocyanidins the immediate products of anthocyanidin synthase? Chem. Commun. (2000) 2473–2474.
3.	Wilmouth, R.C., Turnbull, J.J., Welford, R.W., Clifton, I.J., Prescott, A.G. and Schofield, C.J. Structure and mechanism of anthocyanidin synthase from Arabidopsis thaliana. Structure 10 (2002) 93–103. [DOI] [PMID: 11796114]
4.	Turnbull, J.J., Nagle, M.J., Seibel, J.F., Welford, R.W., Grant, G.H. and Schofield, C.J. The C-4 stereochemistry of leucocyanidin substrates for anthocyanidin synthase affects product selectivity. Bioorg. Med. Chem. Lett. 13 (2003) 3853–3857. [DOI] [PMID: 14552794]
5.	Wellmann, F., Griesser, M., Schwab, W., Martens, S., Eisenreich, W., Matern, U. and Lukacin, R. Anthocyanidin synthase from Gerbera hybrida catalyzes the conversion of (+)-catechin to cyanidin and a novel procyanidin. FEBS Lett. 580 (2006) 1642–1648. [DOI] [PMID: 16494872]

[EC 1.14.20.4 created 2001 as EC 1.14.11.19, transferred 2018 to EC 1.14.20.4]