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
Diverse structures of anthocyanins significantly contribute to flower color, an important floricultural trait in ornamental plants. The 3-O-glucosylated anthocyanins represent the first stable molecules which are further decorated through glycosylation, acylation and methylation involved in fine adjustment and color variation and stabilization [Heller94].
Antocyanidins often occur as sophoroside, i.e. a diglucoside that consists of glucose attached to the 2''-O-position of the 3-O-glucose moiety of anthocyanidins. Such sophoroside, frequently acylated and methylated, are widely found in such plant families as Lamiacea [Terahara01], Convolvulaceae [Terahara04] [Lu92] [Saito93] [Saito95] [Saito05] and Ranunculacea [Saito96] [Saito02]. The anthocyanidin that confers the bright blue color to Ipomoea nil (a member of the Convolvulacea) is a sophoroside that forms a complex with several caffeoyl residues, known as Heavenly Blue antocyanin (HBA). Reddish-brown flowers of dusky mutants of Ipomoea nil contain Wedding Bells anthocyanin (WBA) representing the most favorite flower hue for Japanese floriculturists [Morita05].
Anthocyanidin sophoroside and their derivatives have been demonstrated to exhibit a strong inhibition of maltase when subjected to an α-glucosidase (AGH) inhibitory assay. Acylation of the anthocyanidin sophoroside increased the inhibitory action substantially [Matsui01]. Acylation as a promoting agent has also been shown for the antimutagenicity effect against Salmonella enterica enterica serovar Typhimurium TA 98 caused by anthocyanidin sophoroside [Yoshimoto99] [Yoshimoto01a]. Although anthocyanidin sophoroside and derivatives are induced by UV-B (290-320 nm) and act as protectants UV-A irradiation (320-400 nm) produces a down regulation of those anthocyanins implying complex interactions between UVA and UVB responses that remain to be addressed [Wilson01].
About This Pathway
The crucial step in the formation of anthocyanidin sophoroside as precursors for HBA and WBA in Ipomoea is catalyzed by the anthocyanidin 3-O-glucoside 2-O''-glucosyltransferase (3GGT). The enzyme adds glucose to anthocyanidin 3-glucosides at the 2''-O-position of the glucose moiety forming the corresponding sophorosides. Although the enzyme accepts all three major anthocyanidin 3-O-glucoside, anthocyanidin 3,5-diglucoside are not suitable substrates for the 3GGT [Morita05].
The reddish-brown hue of the flowers (WBA) in mutants of Ipomoea is based on pelargonidin- based anthocyanins whereas the blue flower color (HBA) in this plant has been synthesized from cyanidin-based anthocyanins. It has been found that all the mutants are deficient in a gene that encodes flavonoid 3'-hydroxylase (compare leucopelargonidin and leucocyanidin biosynthesis), involved in the earlier steps towards the biosynthesis of anthocyanins [Hoshino03].
Heller94: Heller W, Forkmann G (1994). "Biosynthesis of flavonoids." In: Harborne JB (editor) The flavonoids. Advances in research since 1986. Chapman & Hall, London Glasgow New York Tokyo Melbourne Madras, 499-537.
Hoshino03: Hoshino A, Morita Y, Choi JD, Saito N, Toki K, Tanaka Y, Iida S (2003). "Spontaneous mutations of the flavonoid 3'-hydroxylase gene conferring reddish flowers in the three morning glory species." Plant Cell Physiol 44(10);990-1001. PMID: 14581624
Matsui01: Matsui T, Ueda T, Oki T, Sugita K, Terahara N, Matsumoto K (2001). "alpha-Glucosidase inhibitory action of natural acylated anthocyanins. 2. alpha-Glucosidase inhibition by isolated acylated anthocyanins." J Agric Food Chem 49(4);1952-6. PMID: 11308352
Morita05: Morita Y, Hoshino A, Kikuchi Y, Okuhara H, Ono E, Tanaka Y, Fukui Y, Saito N, Nitasaka E, Noguchi H, Iida S (2005). "Japanese morning glory dusky mutants displaying reddish-brown or purplish-gray flowers are deficient in a novel glycosylation enzyme for anthocyanin biosynthesis, UDP-glucose:anthocyanidin 3-O-glucoside-2''-O-glucosyltransferase, due to 4-bp insertions in the gene." Plant J 42(3);353-63. PMID: 15842621
Saito05: Saito N, Toki K, Morita Y, Hoshino A, Iida S, Shigihara A, Honda T (2005). "Acylated peonidin glycosides from duskish mutant flowers of Ipomoea nil." Phytochemistry 66(15);1852-60. PMID: 16045946
Saito95: Saito N, Tatsuzawa F, Yoda K, Yokoi M, Kasahara K, Iida S, Shigihara A, Honda T (1995). "Acylated cyanidin glycosides in the violet-blue flowers of Ipomoea purpurea." Phytochemistry 40(4);1283-9. PMID: 7492373
Terahara01: Terahara N, Callebaut A, Ohba R, Nagata T, Ohnishi-Kameyama M, Suzuki M (2001). "Acylated anthocyanidin 3-sophoroside-5-glucosides from Ajuga reptans flowers and the corresponding cell cultures." Phytochemistry 58(3);493-500. PMID: 11557083
Terahara04: Terahara N, Konczak I, Ono H, Yoshimoto M, Yamakawa O (2004). "Characterization of Acylated Anthocyanins in Callus Induced From Storage Root of Purple-Fleshed Sweet Potato, Ipomoea batatas L." J Biomed Biotechnol 2004(5);279-286. PMID: 15577190
Wilson01: Wilson KE, Thompson JE, Huner NP, Greenberg BM (2001). "Effects of ultraviolet-A exposure on ultraviolet-B-induced accumulation of specific flavonoids in Brassica napus." Photochem Photobiol 73(6);678-84. PMID: 11421075
Yoshimoto99: Yoshimoto M, Okuno S, Yoshinaga M, Yamakawa O, Yamaguchi M, Yamada J (1999). "Antimutagenicity of sweetpotato (Ipomoea batatas) roots." Biosci Biotechnol Biochem 63(3);537-41. PMID: 10227139
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