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betalamic acid biosynthesis

General Background Betalains are water-soluble, chromo-alkaloid pigments that replace the anthocyanins in most families of the Caryophyllales order |CITS: [16212790]|. Except for the families Caryophyllaceae and Molluginacea the two subclasses of betalains, i.e. betacyanins and betaxanthins dominate that order and provide violet and yellow cues to flowers, fruits and vegetative tissues, respectively |CITS: [12620337]| |CITS: [16669781]|. Betaxanthins have also been shown to emit green fluorescence which creates contrasting flower color patterns and might serve as signal or guide for pollinators |CITS:[16163341]|. The mutual exclusion of betalains and anthocyanins makes this compound class a useful chemotaxonomic criterion to differentiate families within the Caryophyllales order |CITS: [13831375]|. It appears that both pigment pathways may originate from common ancestors as an anthocyanin like regulator, i.e. MYB1 was identified in Beta vulgaris being able to up- or downregulate betalain biosynthesis |CITS:[25436858]|. The MYB1 in Beta vulgaris has been discussed as being acquired at the time when both pigment pathways were splitting up and is regarded an exciting example for an transcription factor being co-opted out of an existing anthocyanin pathway to regulate the very different betalain pathway instead |CITS:[25547597] [Gerritsen15]|. 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 established |CITS: [MUELLER97A]|. However, their physiological role in fungi remains completely unknown |CITS: [12620337]|. The term 'betalain' had been coined by Wohlpart and Mabry |CITS: [16656788]| to point out the derivation of these pigments from betalamic acid. Although similar in function to the anthocyanins, betalains are structural diverse compounds biosynthesized in a different way. Betalains are induced after pathogenic attacks and wounding |CITS: [STEDDOM03]| and are biosynthetically influenced by light through competing pathways |CITS: [ENDRESS84]|. Betalains are compounds that have found use as colorants in the food industry, the horticultural sector or the agroscience industry |CITS: [11087483]| |CITS: [Stintzing00]|. Recently, they have been considered as potential antioxidants which effectuated intensified corresponding research addressing certain oxidative stress-related disorders in humans |CITS: [11714300]| |CITS: [12405794]| |CITS: [12868496]|. About This Pathway The central intermediate for both betacyanin (|FRAME:PWY-5399|) and betaxanthin biosynthesis (|FRAME:PWY-5404|, |FRAME:PWY-5403|, |FRAME:PWY-5426|) is betalamic acid which derives from 3,4-dihydroxy-L-phenylalanine (DOPA) |CITS:[20467875]|. 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 |CITS: [14730069]|. The common or sugar beet Beta vulgaris is one of the oldest known and richest sources of betalain |CITS:[Keller36]| and was used to identify and biochemically characterize the 4,5-DOPA dioxygenase extradiol encoded by the gene DODA |CITS:[22270561]|. In fungi this enzyme also catalyzes the 2,3-extradiol cleavage of DOPA that produces muscaflavin, indicating a case of convergent evolution of this enzyme |CITS: [Mueller97]| |CITS: [MUELLER97A]|. DOPA may be synthesized through two different pathways from L-tyrosine involving either a bifunctional tyrosinase |CITS: [Steiner99]| or a tyrosine hydroxylase that requires pteridin cofactors for its activity, the latter representing a new enzyme reported for this reaction |CITS: [Yamamoto01]|.

from BIOCYC source record: META_PWY-5394
Type: pathway
Taxonomic scope
conserved biosystem

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