This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Phenylpropanoid Derivatives Biosynthesis → Flavonoids Biosynthesis → Anthocyanins Biosynthesis|
Expected Taxonomic Range: Magnoliophyta
Gentiodelphin, i.e. delphinidin 3-O-glucosyl-5-O-caffeoylglucoside-3'-O-caffeoylglucoside found in the genus Gentiana is a unusual stable anthocyanin conferring deep blue flower colors to this species [Goto82]. The stability of this compound has been proposed as an effect of the intramolecular stacking of acyl residues attached to the opposite sides of the A and B-ring sandwiching the corresponding anthocyanidin [Yoshida91]. The anthocyanidins are self-assembled into chiral supramolecular complexes that have been proposed to contribute to biological functions such as UV protection and specific color variations to attract insects for pollination [Ellestad06].
Research on mono-deacyl derivatives of gentiodelphin, i.e. albireodelphin (acetylated in the A-ring 5-O-glucoside) and mono-deacylgentiodelphin (acytelated in the B-ring 3'-O-glucoside) revealed that the positioning of the caffeoyl residues is vital to stability and coloration of the anthocyanidin. The caffeoyl residue attached to the 3'-O-glucoside of the B-ring contributed more stability through intramolecular stacking and more color development to gentiodelphin than the caffeoyl residue on the A-ring [Yoshida00a].
About This Pathway
The first committed step in the gentiodelphin biosynthesis is the 5-O-glucosylation of delphinidin 3-O-glucoside. The enzyme has been characterized from Perilla frutescens [Yamazaki99] but the activity of the anthocyanin 5-O-glucosyltransferase (5-GT) has also been reported (unpublished results) in crude extracts of Gentiana triflora [Fujiwara97]. Anthocyanin 5-O-glucosyltransferase activity was reported from Gentiana triflora petal extracts, the cDNA cloned and recombinant expressed in Escherichia coli. The catalytic properties of the recombinant enzyme indicate delphinidin-3-O-β-D-glucoside as the preferred substrate and its in vivo activity was also confirmed in transgenic tobacco catalyzing the 5-O-glucosylation of the endogenous cyanidin-3-O-rutinoside yielding cyanidin-3-O-rutinoside-5-O-β-D-glucoside which is not occurring naturally in this plant [Nakatsuka08].
The next steps that further decorate delphinidin 3,5-glucoside with caffeic acid and glucose are proposed to constitute a metabolic grid in the biosynthetic route towards gentiodelphin. Both possible routes, i.e. 3'-O-glucosylation followed by the aromatic 5-O-acylation or vice versa are displayed and thought to be present in Gentiana [Fujiwara98a] [FukuchiMizutani03]. The glucosyltransferases involved in the biosynthesis of gentiodelphin are highly position specific and follow a defined order which is the 3-O-glucosylation followed by the 5-O-glucosylation and the subsequent 3'-O-glucosylation of the delphinidin backbone [FukuchiMizutani03]. Although the function of the anthocyanin 3'-O-glucosyltransferase characterized in Clitoria ternatea (compare ternatin C5 biosynthesis) [Kazuma04] is very similar to the 3'GT involved in the biosynthesis of gentiodelphin (this pathway) there are differences, i.e. substrate preference between those enzymes with regard to the occurrence of acyl groups in the anthocyanidin molecule.
The aromatic acylation with two caffeoyl residues also exhibits strict substrate specificity. The 5-aromatic acyltransferase [Fujiwara97] [Fujiwara98a] can only acylate the 5-O-glucoside but not the 3, 7 or 3' positions of anthocyanins. This enzyme has been located to the cytosol of the outer epidermal cells of petals [Fujiwara98a] which coincides with the location of the 3'-O-glucosyltransferase whose activity has been only found in petals but not in sepals of Gentiana triflora [FukuchiMizutani03]. The aromatic 3'-acyltransferase shaping the final structure of gentiodelphin has not yet been identified and remains to be characterized.
The final step in the gentiodelphin biosynthesis, i.e. the acetylation of the 3'-position of the B-ring has been described in an US patent [Tanaka11]. It has been published that anthocyanin 5-(6'''-hydroxycinnamoyltransferase) [Fujiwara98a] characterized as a 5-acyltransferase is also able to acylate the 3'-position at the B-ring of anthocyanins but no further experimental results have been provided [Mizutani06].
Fujiwara97: Fujiwara H, Tanaka Y, Fukui Y, Nakao M, Ashikari T, Kusumi T (1997). "Anthocyanin 5-aromatic acyltransferase from Gentiana triflora. Purification, characterization and its role in anthocyanin biosynthesis." Eur J Biochem 249(1);45-51. PMID: 9363752
Fujiwara98a: Fujiwara H, Tanaka Y, Yonekura-Sakakibara K, Fukuchi-Mizutani M, Nakao M, Fukui Y, Yamaguchi M, Ashikari T, Kusumi T (1998). "cDNA cloning, gene expression and subcellular localization of anthocyanin 5-aromatic acyltransferase from Gentiana triflora." Plant J 16(4);421-31. PMID: 9881162
FukuchiMizutani03: Fukuchi-Mizutani M, Okuhara H, Fukui Y, Nakao M, Katsumoto Y, Yonekura-Sakakibara K, Kusumi T, Hase T, Tanaka Y (2003). "Biochemical and molecular characterization of a novel UDP-glucose:anthocyanin 3'-O-glucosyltransferase, a key enzyme for blue anthocyanin biosynthesis, from gentian." Plant Physiol 132(3);1652-63. PMID: 12857844
Goto82: Goto T, Kondo T, Tamura H, Imagawa H (1982). "Structure of gentiodelphin, an acylated anthocyanin isolated from Gentiana makinoi, that is stable in dilute aqueous solution." Tetrahedron Letters, 23(36), 3695-3698.
Kazuma04: Kazuma K, Kogawa K, Noda N, Kato N, Suzuki M (2004). "Identification of Delphinidin 3-O-(6''-O-Malonyl)-beta-glucoside-3'-O-beta-glucoside, a Postulated Intermediate in the Biosynthesis of Ternatin C5 in the Blue Petals of Clitoria ternatea (Butterfly Pea)." Chemistry & Bioderversity, 1, 1762-1770.
Nakatsuka08: Nakatsuka T, Sato K, Takahashi H, Yamamura S, Nishihara M (2008). "Cloning and characterization of the UDP-glucose:anthocyanin 5-O-glucosyltransferase gene from blue-flowered gentian." J Exp Bot 59(6);1241-52. PMID: 18375606
Tanaka11: Tanaka Y, Katsumoto Y, Mizutani M, Fukui Y, Togami J (2011). "Stabilization and blueing of anthocyanin pigments using gene encoding aromatic acyltransferase capable of transferring an aromatic acyl group to the 3'-position of anthocyanins." US patent 8,053,634 B2.
Yamazaki99: Yamazaki M, Gong Z, Fukuchi-Mizutani M, Fukui Y, Tanaka Y, Kusumi T, Saito K (1999). "Molecular cloning and biochemical characterization of a novel anthocyanin 5-O-glucosyltransferase by mRNA differential display for plant forms regarding anthocyanin." J Biol Chem 274(11);7405-11. PMID: 10066805
Yoshida00a: Yoshida K, Toyama Y, Kameda K, Kondo T (2000). "Contribution of each caffeoyl residue of the pigment molecule of gentiodelphin to blue color development." Phytochemistry 54(1);85-92. PMID: 10846752
Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216
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