MetaCyc Pathway: betaxanthin biosynthesis (via dopaxanthin)
Inferred from experimentTraceable author statement to experimental support

Pathway diagram: betaxanthin biosynthesis (via dopaxanthin)

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: BiosynthesisSecondary Metabolites BiosynthesisNitrogen-Containing Secondary Compounds BiosynthesisAlkaloids BiosynthesisBetalaine Alkaloids Biosynthesis

Some taxa known to possess this pathway include : Amanita muscaria

Expected Taxonomic Range: Caryophyllales, Fungi

General Background

Betaxanthins represent a subclass of betalains, the nitrogen-containing compounds that replace the anthocyanins in the order of Caryophyllales and some higher fungi [Strack03] [Cai05]. 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 (λ max 470-486 nm) [Christinet04].

Pigments such as anthocyanins and carotenoids are important ecological means to attract pollinators. It could be demonstrated that betalains are equally developed pigments to fill out this physiological function. Betaxanthins are able to fluoresce by absorbing blue light and emitting green light [GandiaHerrero05b]. That implies a complex light-filtering system to create a contrasting fluorescent pattern as violet betacyanins absorb those emitted wavelengths of the yellow betaxanthins. Those findings about fluorescent flowers have been discussed as a new possibility for pollinator perception [GandiaHerrero05c].

About This Pathway

This pathway demonstrates the formation of betaxanthins such as portulacaxanthin II and dopaxanthin by means of non-enzymatic condensation from the amino acids L-tyrosine and L-DOPA, respectively. Tyrosinases have been described as capable to use those betaxanthins [GandiaHerrero05a] 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 [GandiaHerrero05]. 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 [GandiaHerrero05d]. This article also describes miraxanthin III (tyramine as amine moiety) as an alternative substrate for the tyrosinase to form dopamine-betaxanthin, usually derived from the precursor dopamine.

Superpathways: superpathway of betalain biosynthesis

Created 27-Nov-2006 by Foerster H, TAIR


Cai05: Cai Y, Sun M, Corke H (2005). "HPLC characterization of betalains from plants in the amaranthaceae." J Chromatogr Sci 43(9);454-60. PMID: 16212790

Christinet04: 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.

GandiaHerrero05: 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

GandiaHerrero05a: 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

GandiaHerrero05b: Gandia-Herrero F, Escribano J, Garcia-Carmona F (2005). "Betaxanthins as pigments responsible for visible fluorescence in flowers." Planta 222(4);586-93. PMID: 16177911

GandiaHerrero05c: Gandia-Herrero F, Garcia-Carmona F, Escribano J (2005). "Botany: floral fluorescence effect." Nature 437(7057);334. PMID: 16163341

GandiaHerrero05d: 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

Strack03: Strack D, Vogt T, Schliemann W (2003). "Recent advances in betalain research." Phytochemistry 62(3);247-69. PMID: 12620337

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Green05: Green MA, Fry SC (2005). "Vitamin C degradation in plant cells via enzymatic hydrolysis of 4-O-oxalyl-L-threonate." Nature 433(7021);83-7. PMID: 15608627

Kerber08: Kerber, R. C. (2008). ""As simple as possible, but not simpler" - the case of dehydroascorbic acid." J. Chem. Ed. 85(9):1237-1242.

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Mueller96: Mueller LA, Hinz U, Zryd J-P (1996). "Characterization of a tyrosinase from Amanita muscaria involved in betalain biosynthesis." Phvtochemistry, 42(6), 1511-1515.

Simpson00: Simpson GL, Ortwerth BJ (2000). "The non-oxidative degradation of ascorbic acid at physiological conditions." Biochim Biophys Acta 1501(1);12-24. PMID: 10727845

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by Pathway Tools version 19.5 (software by SRI International) on Wed Nov 25, 2015, biocyc12.