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Literature summary extracted from
- Beyond brown polyphenol oxidases as enzymes of plant specialized metabolism (2015), Front. Plant Sci., 5, 1-7 .
Cloned(Commentary)
| EC Number | Cloned (Comment) | Organism |
|---|---|---|
| 1.14.18.1 | gene AS1, DNA and amino acid sequence determination and analyis | Antirrhinum majus |
| 1.14.18.1 | gene AS1, DNA and amino acid sequence determination and analyis | Coreopsis grandiflora |
| 1.14.18.1 | gene PPO, DNA and amino acid sequence determination and analyis | Larrea tridentata |
| 1.14.18.1 | single gene | Juglans regia |
| 1.14.99.47 | gene PPO, DNA and amino acid sequence determination and analyis | Larrea tridentata |
| 1.21.3.6 | gene AS1, DNA and amino acid sequence determination and analyis | Antirrhinum majus |
Protein Variants
| EC Number | Protein Variants | Comment | Organism |
|---|---|---|---|
| 1.14.18.1 | additional information | generation of several PPO-silenced RNAi transgenic lines that show over 95% reduction in catechol oxidase activity relative to wild-type controls, the plants develop a phenotype with disease-like necrotic lesions. Levels of salicylic acid, H2O2, or malondialdehyde are not significantly different in the PPO-silenced leaves compared to wild-type leaves. Metabolomic analysis of PPO-silenced and wild-type leaves reveal significant differences in many metabolites, particularly phenylpropanoids, and about 10fold increased levels of tyramine. Although L-DOPA is undetectable in both PPO-silenced and wild-type walnut plants, levels of dopamine (derived from either L-DOPA or tyramine) and 5,6 dihydroxyindole (derived from L-DOPA) are reduced approximately 6 and 100fold, respectively, in PPO-silenced plants relative to wild-type controls | Juglans regia |
Localization
| EC Number | Localization | Comment | Organism | GeneOntology No. | Textmining |
|---|---|---|---|---|---|
| 1.14.18.1 | chloroplast | - |
Beta vulgaris | 9507 | - |
| 1.14.18.1 | chloroplast | - |
Juglans regia | 9507 | - |
| 1.14.18.1 | chloroplast | - |
Coreopsis grandiflora | 9507 | - |
| 1.14.18.1 | chloroplast | Larrea tridentata PPO contains N-terminal sequences predicting its localization to the chloroplast thylakoid lumen | Larrea tridentata | 9507 | - |
| 1.14.18.1 | thylakoid | - |
Larrea tridentata | 9579 | - |
| 1.14.18.1 | vacuole | - |
Antirrhinum majus | 5773 | - |
| 1.14.99.47 | chloroplast | Larrea tridentata PPO contains N-terminal sequences predicting its localization to the chloroplast thylakoid lumen | Larrea tridentata | 9507 | - |
| 1.14.99.47 | thylakoid | - |
Larrea tridentata | 9579 | - |
| 1.21.3.6 | vacuole | - |
Antirrhinum majus | 5773 | - |
Metals/Ions
| EC Number | Metals/Ions | Comment | Organism | Structure |
|---|---|---|---|---|
| 1.14.18.1 | Cu2+ | a copper-containing enzyme | Beta vulgaris |  |
| 1.14.18.1 | Cu2+ | a copper-containing enzyme | Juglans regia | |
| 1.14.18.1 | Cu2+ | a copper-containing enzyme | Larrea tridentata | |
| 1.14.18.1 | Cu2+ | a copper-containing enzyme | Antirrhinum majus | |
| 1.14.18.1 | Cu2+ | a copper-containing enzyme | Coreopsis grandiflora | |
| 1.14.99.47 | Cu2+ | a copper-containing enzyme | Larrea tridentata | |
| 1.21.3.6 | Cu2+ | a copper-containing enzyme | Neurospora crassa | |
| 1.21.3.6 | Cu2+ | a copper-containing enzyme | Antirrhinum majus | |
Natural Substrates/ Products (Substrates)
| EC Number | Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
|---|---|---|---|---|---|---|---|
| 1.14.18.1 | 2 2',3,4,4',6'-pentahydroxychalcone + O2 | Coreopsis grandiflora | - |
bracteatin + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | Beta vulgaris | - |
2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | Juglans regia | - |
2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | Larrea tridentata | - |
2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | Antirrhinum majus | - |
2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | Coreopsis grandiflora | - |
2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2',4',6',4-tetrahydroxychalcone + O2 | Coreopsis grandiflora | - |
aureusidin + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | Beta vulgaris | - |
dopaquinone + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | Juglans regia | - |
dopaquinone + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | Larrea tridentata | - |
dopaquinone + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | Antirrhinum majus | - |
dopaquinone + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | Coreopsis grandiflora | - |
dopaquinone + H2O | - |
? | |
| 1.14.18.1 | additional information | Juglans regia | In Juglans regia, PPO is encoded by a single gene and has both catechol oxidase activity (oxidation of o-diphenols to their corresponding o-quinones, EC 1.10.3.1) and tyrosinase activity (hydroxylation of monophenols to o-diphenols, EC 1.14.18.1) | ? | - |
? | |
| 1.14.18.1 | additional information | Larrea tridentata | in Juglans regia, PPO is encoded by a single gene and has both catechol oxidase activity (oxidation of o-diphenols to their corresponding o-quinones, EC 1.10.3.1) and tyrosinase activity (hydroxylation of monophenols to o-diphenols, EC 1.14.18.1). The Larrea tridentate PPO gene product acts as a (+)-larreatricin 3'-hydroxylase in vivo | ? | - |
? | |
| 1.14.18.1 | additional information | Beta vulgaris | most plant polphenol oxidases have catechol oxidase activity (oxidation of o-diphenols to their corresponding o-quinones, EC1.10.3.1) and the ability to hydroxylate monophenols to o-diphenols (tyrosinase, EC 1.14.18.1) | ? | - |
? | |
| 1.14.18.1 | additional information | Coreopsis grandiflora | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity result in 3-hydroxylation and formation of the corresponding o-quinone. Besides aurone synthase PPO, a cytochrome P450 chalcone 3-hydroxylase is also involved in the 3-hydroxylation step | ? | - |
? | |
| 1.14.18.1 | additional information | Antirrhinum majus | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity result in 3-hydroxylation and formation of the corresponding o-quinone. Whether aureusidine synthase PPO carries out the 3-hydroxylation reaction in vivo, or whether a cytochrome P450 chalcone 3-hydroxylase is also involved is not definitively established. Aureusidine synthase, EC 1.21.3.6, likely forms the same quinone from 2',3,4,4',6'-pentahydroxychalcone without the need for the 3-hydroxylation step. The resulting quinone is predicted to undergo a 2-step non-enzyme mediated rearrangement to form aureusidin | ? | - |
? | |
| 1.14.99.47 | 3'-hydroxy-larreatricin + O2 | Larrea tridentata | 3-hydroxylation | 3,3'-dihydroxylarreatricin | - |
? | |
| 1.14.99.47 | 3-hydroxy-larreatricin + O2 | Larrea tridentata | 3'-hydroxylation | 3,3'-dihydroxylarreatricin | - |
? | |
| 1.14.99.47 | larreatricin + O2 | Larrea tridentata | 3'-hydroxylation | 3'-hydroxy-larreatricin | - |
? | |
| 1.14.99.47 | larreatricin + O2 | Larrea tridentata | 3-hydroxylation | 3-hydroxy-larreatricin | - |
? | |
| 1.14.99.47 | additional information | Larrea tridentata | the Larrea tridentate PPO gene product acts as a (+)-larreatricin 3'-hydroxylase in vivo | ? | - |
? | |
| 1.21.3.6 | 2 2',3,4,4',6'-pentahydroxychalcone + O2 | Antirrhinum majus | - |
bracteatin + 2 H2O | - |
? | |
| 1.21.3.6 | 2',4',6',4-tetrahydroxychalcone + O2 | Neurospora crassa | - |
aureusidin + H2O | - |
? | |
| 1.21.3.6 | 2',4',6',4-tetrahydroxychalcone + O2 | Antirrhinum majus | - |
aureusidin + H2O | - |
? | |
| 1.21.3.6 | additional information | Antirrhinum majus | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity, EC 1.14.18.1, result in 3-hydroxylation and formation of the corresponding o-quinone. Whether aureusidine synthase PPO carries out the 3-hydroxylation reaction in vivo, or whether a cytochrome P450 chalcone 3-hydroxylase is also involved is not definitively established. Aureusidine synthase likely forms the same quinone from 2',3,4,4',6'-pentahydroxychalcone without the need for the 3-hydroxylation step. The resulting quinone is predicted to undergo a 2-step non-enzyme mediated rearrangement to form aureusidin | ? | - |
? | |
Organism
| EC Number | Organism | UniProt | Comment | Textmining |
|---|---|---|---|---|
| 1.14.18.1 | Antirrhinum majus | Q9FRX6 | - |
- |
| 1.14.18.1 | Beta vulgaris | - |
- |
- |
| 1.14.18.1 | Coreopsis grandiflora | A0A075BX21 | - |
- |
| 1.14.18.1 | Juglans regia | - |
- |
- |
| 1.14.18.1 | Larrea tridentata | Q6UIL3 | - |
- |
| 1.14.18.1 | no activity in Arabidopsis thaliana | - |
- |
- |
| 1.14.99.47 | Larrea tridentata | Q6UIL3 | - |
- |
| 1.21.3.6 | Antirrhinum majus | Q9FRX6 | - |
- |
| 1.21.3.6 | Neurospora crassa | - |
- |
- |
Purification (Commentary)
| EC Number | Purification (Comment) | Organism |
|---|---|---|
| 1.14.18.1 | native enzyme to homogeneity from yellow snapdragon flower buds | Antirrhinum majus |
| 1.14.18.1 | native enzyme to homogeneity from yellow snapdragon flower buds | Coreopsis grandiflora |
| 1.21.3.6 | native enzyme to homogeneity from yellow snapdragon flower buds | Antirrhinum majus |
Source Tissue
| EC Number | Source Tissue | Comment | Organism | Textmining |
|---|---|---|---|---|
| 1.14.18.1 | flower | - |
Antirrhinum majus | - |
| 1.14.18.1 | leaf | - |
Juglans regia | - |
| 1.14.18.1 | root | - |
Beta vulgaris | - |
| 1.14.18.1 | tuber | - |
Beta vulgaris | - |
| 1.21.3.6 | flower | - |
Antirrhinum majus | - |
Substrates and Products (Substrate)
| EC Number | Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|---|
| 1.14.18.1 | 2 2',3,4,4',6'-pentahydroxychalcone + O2 | - |
Coreopsis grandiflora | bracteatin + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | - |
Beta vulgaris | 2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | - |
Juglans regia | 2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | - |
Larrea tridentata | 2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | - |
Antirrhinum majus | 2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2 L-dopa + O2 | - |
Coreopsis grandiflora | 2 dopaquinone + 2 H2O | - |
? | |
| 1.14.18.1 | 2',4',6',4-tetrahydroxychalcone + O2 | - |
Coreopsis grandiflora | aureusidin + H2O | - |
? | |
| 1.14.18.1 | 3'-hydroxy-larreatricin + O2 | 3-hydroxylation | Larrea tridentata | 3,3'-dihydroxylarreatricin | - |
? | |
| 1.14.18.1 | 3-hydroxy-larreatricin + O2 | 3'-hydroxylation | Larrea tridentata | 3,3'-dihydroxylarreatricin | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | - |
Beta vulgaris | dopaquinone + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | - |
Juglans regia | dopaquinone + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | - |
Larrea tridentata | dopaquinone + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | - |
Antirrhinum majus | dopaquinone + H2O | - |
? | |
| 1.14.18.1 | L-tyrosine + O2 | - |
Coreopsis grandiflora | dopaquinone + H2O | - |
? | |
| 1.14.18.1 | larreatricin + O2 | 3'-hydroxylation | Larrea tridentata | 3'-hydroxy-larreatricin | - |
? | |
| 1.14.18.1 | larreatricin + O2 | 3-hydroxylation | Larrea tridentata | 3-hydroxy-larreatricin | - |
? | |
| 1.14.18.1 | additional information | In Juglans regia, PPO is encoded by a single gene and has both catechol oxidase activity (oxidation of o-diphenols to their corresponding o-quinones, EC 1.10.3.1) and tyrosinase activity (hydroxylation of monophenols to o-diphenols, EC 1.14.18.1) | Juglans regia | ? | - |
? | |
| 1.14.18.1 | additional information | in Juglans regia, PPO is encoded by a single gene and has both catechol oxidase activity (oxidation of o-diphenols to their corresponding o-quinones, EC 1.10.3.1) and tyrosinase activity (hydroxylation of monophenols to o-diphenols, EC 1.14.18.1). The Larrea tridentate PPO gene product acts as a (+)-larreatricin 3'-hydroxylase in vivo | Larrea tridentata | ? | - |
? | |
| 1.14.18.1 | additional information | most plant polphenol oxidases have catechol oxidase activity (oxidation of o-diphenols to their corresponding o-quinones, EC1.10.3.1) and the ability to hydroxylate monophenols to o-diphenols (tyrosinase, EC 1.14.18.1) | Beta vulgaris | ? | - |
? | |
| 1.14.18.1 | additional information | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity result in 3-hydroxylation and formation of the corresponding o-quinone. Besides aurone synthase PPO, a cytochrome P450 chalcone 3-hydroxylase is also involved in the 3-hydroxylation step | Coreopsis grandiflora | ? | - |
? | |
| 1.14.18.1 | additional information | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity result in 3-hydroxylation and formation of the corresponding o-quinone. Whether aureusidine synthase PPO carries out the 3-hydroxylation reaction in vivo, or whether a cytochrome P450 chalcone 3-hydroxylase is also involved is not definitively established. Aureusidine synthase, EC 1.21.3.6, likely forms the same quinone from 2',3,4,4',6'-pentahydroxychalcone without the need for the 3-hydroxylation step. The resulting quinone is predicted to undergo a 2-step non-enzyme mediated rearrangement to form aureusidin | Antirrhinum majus | ? | - |
? | |
| 1.14.18.1 | additional information | the purified lenzyme also shows highly enantiospecific larreatricin-3'-hydroxylase activity, EC 1.14.99.47 | Larrea tridentata | ? | - |
? | |
| 1.14.99.47 | 3'-hydroxy-larreatricin + O2 | 3-hydroxylation | Larrea tridentata | 3,3'-dihydroxylarreatricin | - |
? | |
| 1.14.99.47 | 3-hydroxy-larreatricin + O2 | 3'-hydroxylation | Larrea tridentata | 3,3'-dihydroxylarreatricin | - |
? | |
| 1.14.99.47 | larreatricin + O2 | 3'-hydroxylation | Larrea tridentata | 3'-hydroxy-larreatricin | - |
? | |
| 1.14.99.47 | larreatricin + O2 | 3-hydroxylation | Larrea tridentata | 3-hydroxy-larreatricin | - |
? | |
| 1.14.99.47 | additional information | the Larrea tridentate PPO gene product acts as a (+)-larreatricin 3'-hydroxylase in vivo | Larrea tridentata | ? | - |
? | |
| 1.14.99.47 | additional information | the purified larreatricin-3'-hydroxylase catalyzes a highly enantiospecific reaction | Larrea tridentata | ? | - |
? | |
| 1.21.3.6 | 2 2',3,4,4',6'-pentahydroxychalcone + O2 | - |
Antirrhinum majus | bracteatin + 2 H2O | - |
? | |
| 1.21.3.6 | 2',4',6',4-tetrahydroxychalcone + O2 | - |
Neurospora crassa | aureusidin + H2O | - |
? | |
| 1.21.3.6 | 2',4',6',4-tetrahydroxychalcone + O2 | - |
Antirrhinum majus | aureusidin + H2O | - |
? | |
| 1.21.3.6 | additional information | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity, EC 1.14.18.1, result in 3-hydroxylation and formation of the corresponding o-quinone. Whether aureusidine synthase PPO carries out the 3-hydroxylation reaction in vivo, or whether a cytochrome P450 chalcone 3-hydroxylase is also involved is not definitively established. Aureusidine synthase likely forms the same quinone from 2',3,4,4',6'-pentahydroxychalcone without the need for the 3-hydroxylation step. The resulting quinone is predicted to undergo a 2-step non-enzyme mediated rearrangement to form aureusidin | Antirrhinum majus | ? | - |
? | |
Synonyms
| EC Number | Synonyms | Comment | Organism |
|---|---|---|---|
| 1.14.18.1 | aurone synthase | - |
Coreopsis grandiflora |
| 1.14.18.1 | catechol oxidase | - |
Beta vulgaris |
| 1.14.18.1 | catechol oxidase | - |
Juglans regia |
| 1.14.18.1 | catechol oxidase | - |
Larrea tridentata |
| 1.14.18.1 | catechol oxidase | - |
Antirrhinum majus |
| 1.14.18.1 | catechol oxidase | - |
Coreopsis grandiflora |
| 1.14.18.1 | More | cf. EC 1.21.3.6 | Antirrhinum majus |
| 1.14.18.1 | polyphenol oxidase | - |
Beta vulgaris |
| 1.14.18.1 | polyphenol oxidase | - |
Juglans regia |
| 1.14.18.1 | polyphenol oxidase | - |
Larrea tridentata |
| 1.14.18.1 | polyphenol oxidase | - |
Antirrhinum majus |
| 1.14.18.1 | polyphenol oxidase | - |
Coreopsis grandiflora |
| 1.14.18.1 | tyrosinase | - |
Beta vulgaris |
| 1.14.18.1 | tyrosinase | - |
Juglans regia |
| 1.14.18.1 | tyrosinase | - |
Larrea tridentata |
| 1.14.18.1 | tyrosinase | - |
Antirrhinum majus |
| 1.14.18.1 | tyrosinase | - |
Coreopsis grandiflora |
| 1.14.99.47 | larreatricin 3'-hydroxylase | - |
Larrea tridentata |
| 1.14.99.47 | larreatricin 3-hydroxylase | - |
Larrea tridentata |
| 1.14.99.47 | More | cf. EC 1.14.18.1 | Larrea tridentata |
| 1.21.3.6 | AS1 | - |
Antirrhinum majus |
| 1.21.3.6 | aureusidin synthase | - |
Neurospora crassa |
| 1.21.3.6 | aureusidin synthase | - |
Antirrhinum majus |
| 1.21.3.6 | aurone synthase | - |
Antirrhinum majus |
| 1.21.3.6 | More | cf. EC 1.14.18.1 | Neurospora crassa |
| 1.21.3.6 | More | cf. EC 1.14.18.1 | Antirrhinum majus |
General Information
| EC Number | General Information | Comment | Organism |
|---|---|---|---|
| 1.14.18.1 | malfunction | with 95% reduction in catechol oxidase activity relative to wild-type controls, the plants develop a phenotype with disease-like necrotic lesions. Levels of salicylic acid, H2O2, or malondialdehyde are not significantly different in the PPO-silenced leaves compared to wild-type leaves. Metabolomic analysis of PPO-silenced and wild-type leaves reveal significant differences in many metabolites, particularly phenylpropanoids, and about 10fold increased levels of tyramine. Although L-DOPA is undetectable in both PPO-silenced and wild-type walnut plants, levels of dopamine (derived from either L-DOPA or tyramine) and 5,6 dihydroxyindole (derived from L-DOPA) are reduced approximately 6 and 100fold, respectively, in PPO-silenced plants relative to wild-type controls | Juglans regia |
| 1.14.18.1 | metabolism | PPO-mediated conversion of tyrosine to L-DOPA, tyrosine metabolism in walnut, pathway overview | Juglans regia |
| 1.14.18.1 | metabolism | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity result in 3-hydroxylation and formation of the corresponding o-quinone. Besides aurone synthase PPO, a cytochrome P450 chalcone 3-hydroxylase is also involved in the 3-hydroxylation step | Coreopsis grandiflora |
| 1.14.18.1 | metabolism | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity result in 3-hydroxylation and formation of the corresponding o-quinone. Whether aureusidine synthase PPO carries out the 3-hydroxylation reaction in vivo, or whether a cytochrome P450 chalcone 3-hydroxylase is also involved is not definitively established. Aureusidine synthase, EC 1.21.3.6, likely forms the same quinone from 2',3,4,4',6'-pentahydroxychalcone without the need for the 3-hydroxylation step. The resulting quinone is predicted to undergo a 2-step non-enzyme mediated rearrangement to form aureusidine | Antirrhinum majus |
| 1.14.18.1 | metabolism | the enzyme is involved in the first step in betalain biosynthesis, the conversion of tyrosine into L-DOP, i.e. L-3,4-dihydroxyphenylalanine. The resulting L-DOPA can be a substrate for DOPA 4,5-dioxygenase (DODA) that cleaves the aromatic ring to form 4,5-seco-DOPA. The cleavage product spontaneously rearranges to form betalamic acid, which can condense with amino acids or other amine groups to form yellow betaxanthins. Condensation of betalamic acid with cyclo-DOPA forms the red betacyanin pigments. The catechol oxidase activity of PPO is involved in the oxidation of DOPA to DOPA quinone that can spontaneously rearrange to form the cyclo-DOPA moiety of the red betacyanin betalains, pathway overview | Beta vulgaris |
| 1.14.18.1 | metabolism | the tyrosinase activity of PPO is involved in biosynthesis of 8-8'-linked lignans, e.g. nordihydroguaiaretic acid (NDGA), in creosote bush, pathway overview | Larrea tridentata |
| 1.14.18.1 | physiological function | PPOs have a role in postharvest browning, secondary reactions of PPO-generated o-quinones with cellular nucleophiles leading to the familiar discoloration of fresh products and plant materials | Beta vulgaris |
| 1.14.18.1 | physiological function | PPOs have a role in postharvest browning, secondary reactions of PPO-generated o-quinones with cellular nucleophiles leading to the familiar discoloration of fresh products and plant materials | Juglans regia |
| 1.14.18.1 | physiological function | PPOs have a role in postharvest browning, secondary reactions of PPO-generated o-quinones with cellular nucleophiles leading to the familiar discoloration of fresh products and plant materials | Larrea tridentata |
| 1.14.18.1 | physiological function | PPOs have a role in postharvest browning, secondary reactions of PPO-generated o-quinones with cellular nucleophiles leading to the familiar discoloration of fresh products and plant materials. Aurones (aureusidin and bracteatin) are formed from 2,4,6,4-tetrahydroxychalcone or 2,4,6,3,4-pentahydroxychalcone upon incubation with extracts of yellow snapdragon flowers through activity of aureusidin (or aurone) synthase, EC 1.21.3.6 | Antirrhinum majus |
| 1.14.18.1 | physiological function | PPOs have a role in postharvest browning, secondary reactions of PPO-generated o-quinones with cellular nucleophiles leading to the familiar discoloration of fresh products and plant materials. Aurones (aureusidin and bracteatin) are formed from 2,4,6,4-tetrahydroxychalcone or 2,4,6,3,4-pentahydroxychalcone upon incubation with extracts of yellow snapdragon flowers through activity of aureusidin (or aurone) synthase. | Coreopsis grandiflora |
| 1.21.3.6 | metabolism | substrate specificity allows elucidation of a likely mechanism of aurone formation from 2,4,6,4-tetrahydroxychalcone or PHC involving both tyrosinase and catechol oxidase activities of the Antirrhinum majus PPO, pathway overview. Starting with THC, tyrosinase and catechol oxidase activity, EC 1.14.18.1, result in 3-hydroxylation and formation of the corresponding o-quinone. Whether aureusidine synthase PPO carries out the 3-hydroxylation reaction in vivo, or whether a cytochrome P450 chalcone 3-hydroxylase is also involved is not definitively established. Aureusidine synthase likely forms the same quinone from 2',3,4,4',6'-pentahydroxychalcone without the need for the 3-hydroxylation step. The resulting quinone is predicted to undergo a 2-step non-enzyme mediated rearrangement to form aureusidine | Antirrhinum majus |
| 1.21.3.6 | physiological function | PPOs have a role in postharvest browning, secondary reactions of PPO-generated o-quinones with cellular nucleophiles leading to the familiar discoloration of fresh products and plant materials. Aurones (aureusidin and bracteatin) are formed from 2,4,6,4-tetrahydroxychalcone or 2,4,6,3,4-pentahydroxychalcone upon incubation with extracts of yellow snapdragon flowers through activity of aureusidin (or aurone) synthase | Antirrhinum majus |
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