If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Nitrogen-Containing Secondary Compounds Biosynthesis → Alkaloids Biosynthesis → Betalaine Alkaloids Biosynthesis|
Betalains are water-soluble, chromo-alkaloid pigments that replace the anthocyanins in most families of the Caryophyllales order [Cai05]. The two subclasses of betalains, i.e. betacyanins and betaxanthins dominate that order and provide violet and yellow hues to flowers, fruits and vegetative tissues, respectively [Strack03, Grotewold06].
The red to violet betacyanins are the result of the condensation of betalamic acid ( betalamic acid biosynthesis) and cyclo-DOPA to form the aglycon betanidin from which the big majority of natural betacyanins derive (compare betacyanin biosynthesis (via dopamine)). The violet color of betacyanins is based on the observed shift to the corresponding absorbance maximum (λmax 534-554 nm) of the aromatic structure after that condensation [Christinet04a]. In general, the majority of betacyanins are derived from cyclo-DOPA ( betacyanin biosynthesis). However, there are few exceptions that have demonstrated the alternative route of betacyanins derived from the catecholamine dopamine such as 2-descarboxybetanidin and derivatives thereof [Piattelli70, Schliemann99].
Amaranthin belongs to and is the eponym for a major subgroup of betacyanins (see betacyanin biosynthesis) that have mostly been identified in the amaranth family. Only betacyanins contain a glucose moiety that may be further furnished with other molecules such as malonylate and hydroxycinnamic acids.
Betaxanthins represent another subclass of betalains. These pigments are biosynthesized by the condensation of betalamic acid ( betalamic acid biosynthesis) and amino acids/amines forming a Schiff-base that causes the yellow to orange colors (λmax 470-486 nm) [Christinet04a].
Those pigments have also been identified in a restricted number of basidiomycetes such as in the genera Amanita and Hygrocybe. No betacyanin pigments have been found in those fungi but the biosynthesis of several betaxanthin compounds along with other derivatives of betalamic acid such as muscaflavin and muscapurpurin has been confirmed [Mueller97]. However, their physiological role in fungi remains completely unknown [Strack03].
About This Pathway
The central intermediate for both betacyanin ( betacyanin biosynthesis) and betaxanthin biosynthesis ( betaxanthin biosynthesis (via dopaxanthin), betaxanthin biosynthesis (via dopamine), betaxanthin biosynthesis) is betalamic acid which derives from 3,4-dihydroxy-L-phenylalanine (DOPA). The key-enzyme, i.e. the extradiol ring-opening DOPA-4,5-dioxygenase (DODA) catalyzes the formation of 4,5-seco-DOPA in plants which is, in a consecutive reaction, spontaneously converted to the chromophore betalamic acid [Christinet04]. The decisive step in both subclasses to form the corresponding betacyanin- and betaxanthin compounds is a non-enzymatic condensation of betalamic acid with either cyclo-DOPA and derivatives or amino acids/amines, respectively [Schliemann99].
DOPA may be synthesized through two different pathways from L-tyrosine involving either a bifunctional tyrosinase [Steiner99] or a tyrosine hydroxylase that requires pteridin cofactors for its activity, the latter representing a new enzyme reported for this reaction [Yamamoto01].
The observed diversity of betacyanin structures is due to the frequently observed acylation and glucosylation of the aglycone betanidin. The glucosylation of betanidin takes place in a regiospecific way resulting in either the production of betanin (via betanidin 5-O-glucosyltransferase) [Vogt99] or e.g. gomphrenin I (via betanidin 6-O-glucosyltransferase) [Vogt02]. One crucial intermediate in this biosynthesis is cyclo-DOPA that is also a precursor for the further furnishing of betalains. The glucosylated cyclo-DOPA is further metabolized by a rather specific UDP-glucuronic acid: cyclo-DOPA 5-glucoside glucuronosyltransferase that adds glucuronic acid to the structure thus forming amaranthin [Sasaki05a].
It has been demonstrated that the conjugation of a broad variety of amino acids (see betaxanthin biosynthesis (via dopaxanthin)) and amino acid derivatives (e.g. 3-methoxytyramine) with betalamic acid results in the corresponding betaxanthins [Trezzini91]. The first enzymatic step in the pathway is the decarboxylation of aromatic amino acids such as tyrosine or DOPA to form the corresponding amines tyramine and dopamine, respectively [Facchini94, Facchini95].
Tyrosinases have also been described as capable to use certain betaxanthins [GandiaHerrero05b] as substrates for further metabolization. From those results, an alternative pathway has been proposed for the formation of betanidin which involves a tyrosinase activity that converts dopaxanthin into dopaxanthinquinone. Dopaxanthinquinone is than spontaneously cyclisized into betanidin [GandiaHerrero05a]. A similar approach has been undertaken to delineate alternative metabolism for the formation of 2-descarboxy-betanidin (compare betacyanin biosynthesis (via dopamine)) by acting of those tyrosinases on the amine-derived intermediates such as dopamine-betaxanthin to produce the corresponding quinone [GandiaHerrero05].
Subpathways: betalamic acid biosynthesis, betacyanin biosynthesis, amaranthin biosynthesis, betaxanthin biosynthesis (via dopaxanthin), betaxanthin biosynthesis (via dopamine), betaxanthin biosynthesis, betacyanin biosynthesis (via dopamine)
Christinet04: Christinet L, Burdet FX, Zaiko M, Hinz U, Zryd JP (2004). "Characterization and functional identification of a novel plant 4,5-extradiol dioxygenase involved in betalain pigment biosynthesis in Portulaca grandiflora." Plant Physiol 134(1);265-74. PMID: 14730069
Christinet04a: Christinet L (2004). "Characterization and functional identification of a novel plant extradiol 4,5-dioxygenase involved in betalain pigment biosynthesis in Portulaca grandiflora." PhD thesis, Universite de Lausanne, Département de Biologie Moléculaire Végétale.
Facchini95: Facchini PJ, De Luca V (1995). "Phloem-Specific Expression of Tyrosine/Dopa Decarboxylase Genes and the Biosynthesis of Isoquinoline Alkaloids in Opium Poppy." Plant Cell 7(11);1811-1821. PMID: 12242361
GandiaHerrero05: Gandia-Herrero F, Escribano J, Garcia-Carmona F (2005). "Characterization of the monophenolase activity of tyrosinase on betaxanthins: the tyramine-betaxanthin/dopamine-betaxanthin pair." Planta 222(2);307-18. PMID: 15968512
GandiaHerrero05a: Gandia-Herrero F, Escribano J, Garcia-Carmona F (2005). "Betaxanthins as substrates for tyrosinase. An approach to the role of tyrosinase in the biosynthetic pathway of betalains." Plant Physiol 138(1);421-32. PMID: 15805475
GandiaHerrero05b: Gandia-Herrero F, Escribano J, Garcia-Carmona F (2005). "Characterization of the activity of tyrosinase on betaxanthins derived from (R)-amino acids." J Agric Food Chem 53(23);9207-12. PMID: 16277424
Sasaki05a: Sasaki N, Abe Y, Wada K, Koda T, Goda Y, Adachi T, Ozeki Y (2005). "Amaranthin in feather cockscombs is synthesized via glucuronylation at the cyclo-DOPA glucoside step in the betacyanin biosynthetic pathway." J Plant Res 118(6);439-42. PMID: 16247652
Vogt02: Vogt T (2002). "Substrate specificity and sequence analysis define a polyphyletic origin of betanidin 5- and 6-O-glucosyltransferase from Dorotheanthus bellidiformis." Planta 214(3);492-5. PMID: 11855654
Vogt99: Vogt T, Grimm R, Strack D (1999). "Cloning and expression of a cDNA encoding betanidin 5-O-glucosyltransferase, a betanidin- and flavonoid-specific enzyme with high homology to inducible glucosyltransferases from the Solanaceae." Plant J 19(5);509-19. PMID: 10504573
Arita02: Arita DY, Di Marco GS, Schor N, Casarini DE (2002). "Purification and characterization of the active form of tyrosine hydroxylase from mesangial cells in culture." J Cell Biochem 87(1);58-64. PMID: 12210722
Bertocci91: Bertocci B, Miggiano V, Da Prada M, Dembic Z, Lahm HW, Malherbe P (1991). "Human catechol-O-methyltransferase: cloning and expression of the membrane-associated form." Proc Natl Acad Sci U S A 88(4);1416-20. PMID: 1847521
Blau: Blau N, Bonafe L, Thony B "Tetrahydrobiopterin deficiencies without hyperphenylalaninemia: diagnosis and genetics of dopa-responsive dystonia and sepiapterin reductase deficiency." Mol Genet Metab 74(1-2);172-85. PMID: 11592814
Bohm04: Bohm H, Mack G (2004). "Betaxanthin formation and free amino acids in hairy roots of Beta vulgaris var. lutea depending on nutrient medium and glutamate or glutamine feeding." Phytochemistry 65(10);1361-8. PMID: 15231409
Bokern92: Bokern M, Heuer S, Strack D (1992). "Hydroxycinnamic acid transferases in the biosynthesis of acylated betacyanins: Purification and characterization from cell cultures of Chenopodium rubrum and occurrence in some other members of the Caryophyllales." Bot. Acta, 105, 146-151.
Butera02: Butera D, Tesoriere L, Di Gaudio F, Bongiorno A, Allegra M, Pintaudi AM, Kohen R, Livrea MA (2002). "Antioxidant activities of sicilian prickly pear (Opuntia ficus indica) fruit extracts and reducing properties of its betalains: betanin and indicaxanthin." J Agric Food Chem 50(23);6895-901. PMID: 12405794
Cho98: Cho SH, Na JU, Youn H, Hwang CS, Lee CH, Kang SO (1998). "Tepidopterin, 1-O-(L-threo-biopterin-2'-yl)-beta-N-acetylglucosamine from Chlorobium tepidum." Biochim Biophys Acta 1379(1);53-60. PMID: 9468332
Chung00: Chung HJ, Kim YA, Kim YJ, Choi YK, Hwang YK, Park YS (2000). "Purification and characterization of UDP-glucose:tetrahydrobiopterin glucosyltransferase from Synechococcus sp. PCC 7942." Biochim Biophys Acta 1524(2-3);183-8. PMID: 11113566
El83: El Mestikawy S, Glowinski J, Hamon M (1983). "Tyrosine hydroxylase activation in depolarized dopaminergic terminals--involvement of Ca2+-dependent phosphorylation." Nature 302(5911);830-2. PMID: 6133218
Facchini94a: Facchini, Peter, De Luca, Vincenzo "Differential and tissue-specific expression of a gene family for tyrosine/dopa decarboxylase in Opium poppy." The journal of biological chemistry (1994) 269(43):26684-26690.
Facchini95a: Facchini PJ, De Luca V (1995). "Expression in Escherichia coli and partial characterization of two tyrosine/dopa decarboxylases from opium poppy." Phytochemistry 38(5);1119-26. PMID: 7766394
GandiaHerrero04: Gandia-Herrero F, Garcia-Carmona F, Escribano J (2004). "Purification and characterization of a latent polyphenol oxidase from beet root (Beta vulgaris L.)." J Agric Food Chem 52(3);609-15. PMID: 14759157
GandiaHerrero12: Gandia-Herrero F, Garcia-Carmona F (2012). "Characterization of recombinant Beta vulgaris 4,5-DOPA-extradiol-dioxygenase active in the biosynthesis of betalains." Planta 236(1);91-100. PMID: 22270561
Showing only 20 references. To show more, press the button "Show all references".
©2016 SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493