Reaction participants Show >> << Hide
- Name help_outline a 3'-unsubstituted flavone Identifier CHEBI:138726 Charge 0 Formula C15HO2R9 SMILEShelp_outline C1(=C(C(=C(C2=C1OC(=C(C2=O)*)C3=C(C(=C(C(=C3*)*)*)[H])*)*)*)*)* 2D coordinates Mol file for the small molecule Search links Involved in 1 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline O2 Identifier CHEBI:15379 (CAS: 7782-44-7) help_outline Charge 0 Formula O2 InChIKeyhelp_outline MYMOFIZGZYHOMD-UHFFFAOYSA-N SMILEShelp_outline O=O 2D coordinates Mol file for the small molecule Search links Involved in 2,648 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
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Namehelp_outline
reduced [NADPH—hemoprotein reductase]
Identifier
RHEA-COMP:11964
Reactive part
help_outline
- Name help_outline FMNH2 Identifier CHEBI:57618 (Beilstein: 6258176) help_outline Charge -2 Formula C17H21N4O9P InChIKeyhelp_outline YTNIXZGTHTVJBW-SCRDCRAPSA-L SMILEShelp_outline Cc1cc2Nc3c([nH]c(=O)[nH]c3=O)N(C[C@H](O)[C@H](O)[C@H](O)COP([O-])([O-])=O)c2cc1C 2D coordinates Mol file for the small molecule Search links Involved in 771 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline a 3'-hydroxyflavone Identifier CHEBI:27741 Charge 0 Formula C15HO3R9 SMILEShelp_outline Oc1c([*])c([*])c([*])c(c1[*])-c1oc2c([*])c([*])c([*])c([*])c2c(=O)c1[*] 2D coordinates Mol file for the small molecule Search links Involved in 3 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H+ Identifier CHEBI:15378 Charge 1 Formula H InChIKeyhelp_outline GPRLSGONYQIRFK-UHFFFAOYSA-N SMILEShelp_outline [H+] 2D coordinates Mol file for the small molecule Search links Involved in 9,176 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H2O Identifier CHEBI:15377 (Beilstein: 3587155; CAS: 7732-18-5) help_outline Charge 0 Formula H2O InChIKeyhelp_outline XLYOFNOQVPJJNP-UHFFFAOYSA-N SMILEShelp_outline [H]O[H] 2D coordinates Mol file for the small molecule Search links Involved in 6,048 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
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Namehelp_outline
oxidized [NADPH—hemoprotein reductase]
Identifier
RHEA-COMP:11965
Reactive part
help_outline
- Name help_outline FMN Identifier CHEBI:58210 Charge -3 Formula C17H18N4O9P InChIKeyhelp_outline ANKZYBDXHMZBDK-SCRDCRAPSA-K SMILEShelp_outline C12=NC([N-]C(C1=NC=3C(N2C[C@@H]([C@@H]([C@@H](COP(=O)([O-])[O-])O)O)O)=CC(=C(C3)C)C)=O)=O 2D coordinates Mol file for the small molecule Search links Involved in 781 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
RHEA:16337 | RHEA:16338 | RHEA:16339 | RHEA:16340 | |
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Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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Related reactions help_outline
Specific form(s) of this reaction
Publications
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Completion of tricin biosynthesis pathway in rice: cytochrome P450 75B4 is a unique chrysoeriol 5'-hydroxylase.
Lam P.Y., Liu H., Lo C.
Flavones are ubiquitously accumulated in land plants, but their biosynthesis in monocots remained largely elusive until recent years. Recently, we demonstrated that the rice (Oryza sativa) cytochrome P450 enzymes CYP93G1 and CYP93G2 channel flavanones en route to flavone O-linked conjugates and C- ... >> More
Flavones are ubiquitously accumulated in land plants, but their biosynthesis in monocots remained largely elusive until recent years. Recently, we demonstrated that the rice (Oryza sativa) cytochrome P450 enzymes CYP93G1 and CYP93G2 channel flavanones en route to flavone O-linked conjugates and C-glycosides, respectively. In tricin, the 3',5'-dimethoxyflavone nucleus is formed before O-linked conjugations. Previously, flavonoid 3',5'-hydroxylases belonging to the CYP75A subfamily were believed to generate tricetin from apigenin for 3',5'-O-methylation to form tricin. However, we report here that CYP75B4 a unique flavonoid B-ring hydroxylase indispensable for tricin formation in rice. A CYP75B4 knockout mutant is tricin deficient, with unusual accumulation of chrysoeriol (a 3'-methoxylated flavone). CYP75B4 functions as a bona fide flavonoid 3'-hydroxylase by restoring the accumulation of 3'-hydroxylated flavonoids in Arabidopsis (Arabidopsis thaliana) transparent testa7 mutants and catalyzing in vitro 3'-hydroxylation of different flavonoids. In addition, overexpression of both CYP75B4 and CYP93G1 (a flavone synthase II) in Arabidopsis resulted in tricin accumulation. Specific 5'-hydroxylation of chrysoeriol to selgin by CYP75B4 was further demonstrated in vitro. The reaction steps leading to tricin biosynthesis are then reconstructed as naringenin → apigenin → luteolin → chrysoeriol → selgin → tricin. Hence, chrysoeriol, instead of tricetin, is an intermediate in tricin biosynthesis. CYP75B4 homologous sequences are highly conserved in Poaceae, and they are phylogenetically distinct from the canonical CYP75B flavonoid 3'-hydroxylase sequences. Recruitment of chrysoeriol-specific 5'-hydroxylase activity by an ancestral CYP75B sequence may represent a key event leading to the prevalence of tricin-derived metabolites in grasses and other monocots today. << Less
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Functional characterization of key structural genes in rice flavonoid biosynthesis.
Shih C.H., Chu H., Tang L.K., Sakamoto W., Maekawa M., Chu I.K., Wang M., Lo C.
Rice is a model system for monocot but the molecular features of rice flavonoid biosynthesis have not been extensively characterized. Rice structural gene homologs encoding chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), flavonoid 3'-hydroxylase (F3'H), dihydrofla ... >> More
Rice is a model system for monocot but the molecular features of rice flavonoid biosynthesis have not been extensively characterized. Rice structural gene homologs encoding chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), flavonoid 3'-hydroxylase (F3'H), dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase (ANS) were identified by homology searches. Unique differential expression of OsF3H, OsDFR, and OsANS1 controlled by the Pl(w) locus, which contains the R/B-type regulatory genes OSB1 and OSB2, was demonstrated during light-induced anthocyanin accumulation in T65-Plw seedlings. Previously, F3H genes were often considered as early genes co-regulated with CHS and CHI genes in other plants. In selected non-pigmented rice lines, OSB2 is not expressed following illumination while their expressed OSB1sequences all contain the same nucleotide change leading to the T(64) M substitution within the conserved N-terminal interacting domain. Furthermore, the biochemical roles of the expressed rice structural genes (OsCHS1, OsCHI, OsF3H, and OsF3'H) were established in planta for the first time by complementation in the appropriate Arabidopsis transparent testa mutants. Using yeast two-hybrid analysis, OsCHS1 was demonstrated to interact physically with OsF3H, OsF3'H, OsDFR, and OsANS1, suggesting the existence of a macromolecular complex for anthocyanin biosynthesis in rice. Finally, flavones were identified as the major flavonoid class in the non-pigmented T65 seedlings in which the single-copy OsF3H gene was not expressed. Competition between flavone and anthocyanin pathways was evidenced by the significant reduction of tricin accumulation in the T65-Plw seedlings. << Less