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. Author manuscript; available in PMC: 2017 Jun 1.
Published in final edited form as: Phytochem Rev. 2016 Mar 11;15(3):425–444. doi: 10.1007/s11101-016-9459-z

Figure 2.

Figure 2

a) A mechanism for quercetinase-mediated conversion of quercetin (2.1) into 2-protocatechuoylphloroglucinolcarboxylic acid (2.5) adapted from (Schaab, Barney, Francisco, 2006). Decarboxylation of 1,3,5-trihydroxybenzoic acid (2.7) into phloroglucinol (2.8) is not mediated by quercetinase. b) The co-crystal structure of Aspergillus japonicus quercetinase 2,3 dioxygenase complexed with the natural substrate quercetin under anaerobic condition is available (pdb 1H1I). The X-ray structure shows that the flavonol coordinates to the copper ion through the C-ring OH group at position 3 (Steiner, Kalk, Dijkstra, 2002).