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superpathway of anthocyanin biosynthesis (from cyanidin and cyanidin 3-O-glucoside)

General Background The superpathway of anthocyanin biosynthesis that originates from cyanidin and cyanidin 3-O-glucoside comprises the formation of compounds such as rose anthocyanin, anthocyanidin sophoroside and shisonin. Those anthocyanins are flower pigments that contribute to a wide variation of colors in many species representing various structures that range from simple anthocyanin diglucosides to more complex polyacylated anthocyanins. Rose anthocyanins are based on the simple structure of cyanidin 3,5-diglucoside. This anthocyanin is obviously potent enough to provide the wide spectrum of colors found in roses. Like the anthocyanidin 3-glucoside in other plants (compare :PWY-5125 anthocyanin biosynthesis (pelargonidin 3-O-glucoside, cyanidin 3-O-glucoside), :PWY-5153 anthocyanin biosynthesis (delphinidin 3-O-glucoside)) the anthocyanidin 3,5-diglucoside constitutes the first stable anthocyanin in roses and contributes to its solubility in the vacuole . Insofar the pathway described here is unique to the rose family. 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. 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 :CPD-7841 Wedding Bells Anthocyanin (HBA). Reddish-brown flowers of dusky mutants of Ipomoea nil contain :CPD-7840 Heavenly Blue Antocyanin (WBA) representing the most favorite flower hue for Japanese floriculturists . Shisonin, a mono-malonylated anthocyanin, has been found in high amounts in Labiatae. Together with the bi-malonylated anthocyanin salvianin (:PWY-5268 salvianin biosynthesis) shisonin constitutes a major flower pigment in that genus . Both anthocyanins occur predominantly in different species, i.e. shisonin in Perilla and salvianin in Salvia and share key enzymatic steps of their respective biosyntheses comprising glucosylation and aromatic and aliphatic acylation. About This Pathway Rose anthocyanin The formation of cyanidin 3,5-diglucoside in roses is catalyzed by a distinctive enzyme that is able to glucosylate both the flavonoid A-ring 5-O-position and the 3-O-position of the flavonoid C-ring. In contrast to the two single glucosyltransferases involved in the generation of anthocyanin 3,5-diglucoside in other plants this unique enzyme possesses both catalytic activities and also changes the order of glucosylation . The first intermediate in this pathway is the unstable anthocyanidin-5-O-glucoside which is subsequently further glucosylated to form the stable cyanidin 3,5-diglucoside. Anthocyanin sophoroside 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 . Shisonin The formation of shisonin, the precursor for the aliphatic acylation with malonyl-CoA to form malonylshisonin is carried out by 3-aromatic acylation of cyanindin 3-O-glucoside with p-coumaric acid followed by the 5-O-glucosylation of the anthocyanin. The exact biosynthetic route towards shisonin is still a matter of debate and the actual succession of 5-O-glucosylation and 3-O-acylation remains to be demonstrated. The anthocyanin-5-O-glucoside-6'''-O-malonyltransferase that produces malonylshisonin expresses a high affinity towards both pelargonidin (salvianin biosynthesis) and cyanidin (shisonin biosynthesis) derived anthocyanidin intermediates forming the corresponding aromatic and aliphatic acylated compounds.

from BIOCYC source record: ARA_PWY-5313
Type: pathway
Taxonomic scope
organism-specific biosystem

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