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Stephen G Bell - One of the best experts on this subject based on the ideXlab platform.
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cytochrome p450 cyp199a4 from rhodopseudomonas palustris catalyzes heteroatom dealkylations sulfoxidation and amide and cyclic hemiacetal formation
ACS Catalysis, 2018Co-Authors: T Coleman, James J De Voss, John B. Bruning, Siew Hoon Wong, M N Podgorski, Stephen G BellAbstract:The cytochrome P450 enzymes execute a range of selective oxidative biotransformations across many biological systems. The bacterial enzyme CYP199A4 catalyzes the oxidative demethylation of 4-Methoxybenzoic Acid. The benzoic Acid moiety of the molecule binds in the active site of the enzyme such that the functional group at the para-position is held close to the heme iron. Therefore, CYP199A4 has the potential to catalyze alternative monooxygenase reactions with different para-substituted benzoic Acid substrates such as thioethers and alkylamines. The oxidation of 4-methyl- and 4-ethyl-thiobenzoic Acids by CYP199A4 resulted in sulfur oxidation. 4-Ethylthiobenzoic Acid sulfoxidation and 4-ethylbenzoic Acid hydroxylation by CYP199A4 occurred with high enantioselectivity (>74% enantiomeric excess). By way of contrast, CYP199A4 catalyzed exclusive oxidative N-demethylation over N-oxide formation with 4-methyl- and 4-dimethylaminobenzoic Acids. Unexpectedly acetamide formation by CYP199A4 competes with dealkyla...
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the importance of the benzoic Acid carboxylate moiety for substrate recognition by cyp199a4 from rhodopseudomonas palustris haa2
Biochimica et Biophysica Acta, 2016Co-Authors: T Coleman, Rebecca R Chao, James J De Voss, Stephen G BellAbstract:Abstract Background The cytochrome P450 enzyme CYP199A4 can efficiently demethylate 4-Methoxybenzoic Acid. The substrate is positioned in the enzyme active site with the methoxy group ideally positioned for demethylation. This occurs through interactions of hydrophobic benzene ring with aromatic phenylalanine residues and the charged carboxylate group with polar and basic amino Acids. Methods In vitro substrate binding and kinetic turnover assays coupled with HPLC and GC–MS analysis and whole-cell oxidation turnovers. Results Modification of the carboxylate group to an amide or aldehyde resulted in substrate binding, as judged by the almost total shift of the spin state to the high-spin form, but binding was three orders of magnitude weaker. Changing the carboxylate to phenol alcohol, ketone, ester and nitro groups and boronic, sulfinic and sulfonic Acids resulted in a dramatic reduction in the binding affinity. Even phenylacetic Acids were mediocre substrates for CYP199A4, despite maintaining a carboxylate group. The weaker binding of all of these substrates results in lower levels of turnover activity and product formation compared to 4-Methoxybenzoic Acid. Conclusion Substrate binding to CYP199A4 is tightly regulated by interactions between the 4-Methoxybenzoic Acid and the amino Acids in the active site. The benzoic Acid carboxylate moiety is critical for optimal substrate binding and turnover activity with CYP199A4. General significance An understanding of how the CYP199A4 enzyme has evolved to be highly selective for para -substituted benzoic Acids. This provides valuable insight into how other, as yet structurally uncharacterised, monooxygenase enzymes may bind benzoic Acid substrates.
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CYP199A4 catalyses the efficient demethylation and demethenylation of para-substituted benzoic Acid derivatives
RSC Advances, 2015Co-Authors: T Coleman, Rebecca R Chao, James J De Voss, John B. Bruning, Stephen G BellAbstract:The cytochrome P450 enzyme CYP199A4, from Rhodopseudomonas palustris strain HaA2, can efficiently demethylate 4-Methoxybenzoic Acid via hemiacetal formation and subsequent elimination of formaldehyde. Oxidative demethylation of a methoxy group para to the carboxyl moiety is strongly favoured over reaction at one in the ortho or meta positions. Dimethoxybenzoic Acids containing a para-methoxy group were also efficiently demethylated exclusively at the para position. The presence of additional methoxy substituents reduces the substrate binding affinity and the activity compared to 4-Methoxybenzoic Acid. The addition of the smaller hydroxy group to the ortho or meta positions or of a nitrogen heteroatom in the aromatic ring of the 4-methoxybenzoate skeleton was better tolerated by the enzyme and these analogues were also readily demethylated. There was no evidence of methylenedioxy ring formation with 3-hydroxy-4-Methoxybenzoic Acid, an activity which is observed with certain plant CYP enzymes with analogous substrates. CYP199A4 is also able to deprotect the methylenedioxy group of 3,4-(methylenedioxy)benzoic Acid to yield 3,4-dihydroxybenzoic Acid and formic Acid. This study defines the substrate range of CYP199A4 and reveals that substrates without a para substituent are not oxidised with any significant activity. Therefore para-substituted benzoic Acids are ideal substrate scaffolds for the CYP199A4 enzyme and will aid in the design of optimised probes to investigate the mechanism of this class of enzymes. They also allow an assessment of the potential of CYP199A4 for synthetic biocatalytic processes involving selective oxidative demethylation or demethenylation.
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Investigation of the Substrate Range of CYP199A4: Modification of the Partition between Hydroxylation and Desaturation Activities by Substrate and Protein Engineering
Chemistry (Weinheim an der Bergstrasse Germany), 2012Co-Authors: Stephen G Bell, Ruimin Zhou, Wen Yang, Adrian B. H. Tan, Alexander S. Gentleman, Luet-lok Wong, Weihong ZhouAbstract:The cytochrome P450 enzyme CYP199A4, from Rhodopseudomonas palustris HaA2, can efficiently demethylate 4-Methoxybenzoic Acid. It is also capable of oxidising a range of other related substrates. By investigating substrates with different substituents and ring systems we have been able to show that the carboxylate group and the nature of the ring system and the substituent are all important for optimal substrate binding and activity. The structures of the veratric Acid, 2-naphthoic Acid and indole-6-carboxylic Acid substrate-bound CYP199A4 complexes reveal the substrate binding modes and the side-chain conformational changes of the active site residues to accommodate these larger substrates. They also provide a rationale for the selectivity of product oxidation. The oxidation of alkyl substituted benzoic Acids by CYP199A4 is more complex, with desaturation reactions competing with hydroxylation activity. The structure of 4-ethylbenzoic Acid-bound CYP199A4 revealed that the substrate is held in a similar position to 4-Methoxybenzoic Acid, and that the Cβ CH bonds of the ethyl group are closer to the heme iron than those of the Cα (3.5 vs. 4.8 A). This observation, when coupled to the relative energies of the reaction intermediates, indicates that the positioning of the alkyl group relative to the heme iron may be critical in determining the amount of desaturation that is observed. By mutating a single residue in the active site of CYP199A4 (Phe185) we were able to convert the enzyme into a 4-ethylbenzoic Acid desaturase.
Leonardo Palmisano - One of the best experts on this subject based on the ideXlab platform.
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Home-prepared anatase, rutile, and brookite TiO2 for selective photocatalytic oxidation of 4-methoxybenzyl alcohol in water: reactivity and ATR-FTIR study
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2009Co-Authors: Vincenzo Augugliaro, Vittorio Loddo, María José López-muñoz, Carlos Márquez-Álvarez, Giovanni Palmisano, Leonardo Palmisano, Sedat YurdakalAbstract:TiO2 catalysts of anatase, rutile and brookite phase were prepared at low temperature and tested for carrying out the photocatalytic partial oxidation of 4-methoxybenzyl alcohol to 4-methoxybenzaldehyde (p-anisaldehyde) in organic-free water suspensions. Traces of 4-Methoxybenzoic Acid and open-ring products were the only by-products present, CO2 being the other main oxidation product. Rutile exhibited the highest yield to p-anisaldehyde (62% mol) at a rate of the same order of magnitude of that showed by the other samples. Commercial rutile and anatase photocatalysts were also used for the sake of comparison. The samples have been characterised by an in situ ATR-FTIR investigation carried out in conditions simulating the photoreaction ones.
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photocatalytic selective oxidation of 4 methoxybenzyl alcohol to aldehyde in aqueous suspension of home prepared titanium dioxide catalyst
Advanced Synthesis & Catalysis, 2007Co-Authors: Giovanni Palmisano, Vincenzo Augugliaro, Vittorio Loddo, Sedat Yurdakal, Leonardo PalmisanoAbstract:The photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde (PAA) was performed in water with organic-free suspensions of home-prepared and commercial titanium dioxide (TiO 2 ) catalysts. The nanostructured TiO 2 samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl 4 ), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4-methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5 % mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116%. A comparison with two commercial TiO 2 samples showed that all the home-prepared catalysts exhibited a PAA yield higher than that of commercial ones. The only by-products present were traces of 4-Methoxybenzoic Acid and aliphatic products, carbon dioxide being the other main oxidation product.
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Photocatalytic Selective Oxidation of 4‐Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home‐Prepared Titanium Dioxide Catalyst
Advanced Synthesis & Catalysis, 2007Co-Authors: Giovanni Palmisano, Vincenzo Augugliaro, Vittorio Loddo, Sedat Yurdakal, Leonardo PalmisanoAbstract:The photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde (PAA) was performed in water with organic-free suspensions of home-prepared and commercial titanium dioxide (TiO 2 ) catalysts. The nanostructured TiO 2 samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl 4 ), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4-methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5 % mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116%. A comparison with two commercial TiO 2 samples showed that all the home-prepared catalysts exhibited a PAA yield higher than that of commercial ones. The only by-products present were traces of 4-Methoxybenzoic Acid and aliphatic products, carbon dioxide being the other main oxidation product.
T Coleman - One of the best experts on this subject based on the ideXlab platform.
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cytochrome p450 cyp199a4 from rhodopseudomonas palustris catalyzes heteroatom dealkylations sulfoxidation and amide and cyclic hemiacetal formation
ACS Catalysis, 2018Co-Authors: T Coleman, James J De Voss, John B. Bruning, Siew Hoon Wong, M N Podgorski, Stephen G BellAbstract:The cytochrome P450 enzymes execute a range of selective oxidative biotransformations across many biological systems. The bacterial enzyme CYP199A4 catalyzes the oxidative demethylation of 4-Methoxybenzoic Acid. The benzoic Acid moiety of the molecule binds in the active site of the enzyme such that the functional group at the para-position is held close to the heme iron. Therefore, CYP199A4 has the potential to catalyze alternative monooxygenase reactions with different para-substituted benzoic Acid substrates such as thioethers and alkylamines. The oxidation of 4-methyl- and 4-ethyl-thiobenzoic Acids by CYP199A4 resulted in sulfur oxidation. 4-Ethylthiobenzoic Acid sulfoxidation and 4-ethylbenzoic Acid hydroxylation by CYP199A4 occurred with high enantioselectivity (>74% enantiomeric excess). By way of contrast, CYP199A4 catalyzed exclusive oxidative N-demethylation over N-oxide formation with 4-methyl- and 4-dimethylaminobenzoic Acids. Unexpectedly acetamide formation by CYP199A4 competes with dealkyla...
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the importance of the benzoic Acid carboxylate moiety for substrate recognition by cyp199a4 from rhodopseudomonas palustris haa2
Biochimica et Biophysica Acta, 2016Co-Authors: T Coleman, Rebecca R Chao, James J De Voss, Stephen G BellAbstract:Abstract Background The cytochrome P450 enzyme CYP199A4 can efficiently demethylate 4-Methoxybenzoic Acid. The substrate is positioned in the enzyme active site with the methoxy group ideally positioned for demethylation. This occurs through interactions of hydrophobic benzene ring with aromatic phenylalanine residues and the charged carboxylate group with polar and basic amino Acids. Methods In vitro substrate binding and kinetic turnover assays coupled with HPLC and GC–MS analysis and whole-cell oxidation turnovers. Results Modification of the carboxylate group to an amide or aldehyde resulted in substrate binding, as judged by the almost total shift of the spin state to the high-spin form, but binding was three orders of magnitude weaker. Changing the carboxylate to phenol alcohol, ketone, ester and nitro groups and boronic, sulfinic and sulfonic Acids resulted in a dramatic reduction in the binding affinity. Even phenylacetic Acids were mediocre substrates for CYP199A4, despite maintaining a carboxylate group. The weaker binding of all of these substrates results in lower levels of turnover activity and product formation compared to 4-Methoxybenzoic Acid. Conclusion Substrate binding to CYP199A4 is tightly regulated by interactions between the 4-Methoxybenzoic Acid and the amino Acids in the active site. The benzoic Acid carboxylate moiety is critical for optimal substrate binding and turnover activity with CYP199A4. General significance An understanding of how the CYP199A4 enzyme has evolved to be highly selective for para -substituted benzoic Acids. This provides valuable insight into how other, as yet structurally uncharacterised, monooxygenase enzymes may bind benzoic Acid substrates.
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CYP199A4 catalyses the efficient demethylation and demethenylation of para-substituted benzoic Acid derivatives
RSC Advances, 2015Co-Authors: T Coleman, Rebecca R Chao, James J De Voss, John B. Bruning, Stephen G BellAbstract:The cytochrome P450 enzyme CYP199A4, from Rhodopseudomonas palustris strain HaA2, can efficiently demethylate 4-Methoxybenzoic Acid via hemiacetal formation and subsequent elimination of formaldehyde. Oxidative demethylation of a methoxy group para to the carboxyl moiety is strongly favoured over reaction at one in the ortho or meta positions. Dimethoxybenzoic Acids containing a para-methoxy group were also efficiently demethylated exclusively at the para position. The presence of additional methoxy substituents reduces the substrate binding affinity and the activity compared to 4-Methoxybenzoic Acid. The addition of the smaller hydroxy group to the ortho or meta positions or of a nitrogen heteroatom in the aromatic ring of the 4-methoxybenzoate skeleton was better tolerated by the enzyme and these analogues were also readily demethylated. There was no evidence of methylenedioxy ring formation with 3-hydroxy-4-Methoxybenzoic Acid, an activity which is observed with certain plant CYP enzymes with analogous substrates. CYP199A4 is also able to deprotect the methylenedioxy group of 3,4-(methylenedioxy)benzoic Acid to yield 3,4-dihydroxybenzoic Acid and formic Acid. This study defines the substrate range of CYP199A4 and reveals that substrates without a para substituent are not oxidised with any significant activity. Therefore para-substituted benzoic Acids are ideal substrate scaffolds for the CYP199A4 enzyme and will aid in the design of optimised probes to investigate the mechanism of this class of enzymes. They also allow an assessment of the potential of CYP199A4 for synthetic biocatalytic processes involving selective oxidative demethylation or demethenylation.
Giovanni Palmisano - One of the best experts on this subject based on the ideXlab platform.
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Home-prepared anatase, rutile, and brookite TiO2 for selective photocatalytic oxidation of 4-methoxybenzyl alcohol in water: reactivity and ATR-FTIR study
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2009Co-Authors: Vincenzo Augugliaro, Vittorio Loddo, María José López-muñoz, Carlos Márquez-Álvarez, Giovanni Palmisano, Leonardo Palmisano, Sedat YurdakalAbstract:TiO2 catalysts of anatase, rutile and brookite phase were prepared at low temperature and tested for carrying out the photocatalytic partial oxidation of 4-methoxybenzyl alcohol to 4-methoxybenzaldehyde (p-anisaldehyde) in organic-free water suspensions. Traces of 4-Methoxybenzoic Acid and open-ring products were the only by-products present, CO2 being the other main oxidation product. Rutile exhibited the highest yield to p-anisaldehyde (62% mol) at a rate of the same order of magnitude of that showed by the other samples. Commercial rutile and anatase photocatalysts were also used for the sake of comparison. The samples have been characterised by an in situ ATR-FTIR investigation carried out in conditions simulating the photoreaction ones.
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photocatalytic selective oxidation of 4 methoxybenzyl alcohol to aldehyde in aqueous suspension of home prepared titanium dioxide catalyst
Advanced Synthesis & Catalysis, 2007Co-Authors: Giovanni Palmisano, Vincenzo Augugliaro, Vittorio Loddo, Sedat Yurdakal, Leonardo PalmisanoAbstract:The photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde (PAA) was performed in water with organic-free suspensions of home-prepared and commercial titanium dioxide (TiO 2 ) catalysts. The nanostructured TiO 2 samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl 4 ), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4-methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5 % mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116%. A comparison with two commercial TiO 2 samples showed that all the home-prepared catalysts exhibited a PAA yield higher than that of commercial ones. The only by-products present were traces of 4-Methoxybenzoic Acid and aliphatic products, carbon dioxide being the other main oxidation product.
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Photocatalytic Selective Oxidation of 4‐Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home‐Prepared Titanium Dioxide Catalyst
Advanced Synthesis & Catalysis, 2007Co-Authors: Giovanni Palmisano, Vincenzo Augugliaro, Vittorio Loddo, Sedat Yurdakal, Leonardo PalmisanoAbstract:The photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde (PAA) was performed in water with organic-free suspensions of home-prepared and commercial titanium dioxide (TiO 2 ) catalysts. The nanostructured TiO 2 samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl 4 ), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4-methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5 % mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116%. A comparison with two commercial TiO 2 samples showed that all the home-prepared catalysts exhibited a PAA yield higher than that of commercial ones. The only by-products present were traces of 4-Methoxybenzoic Acid and aliphatic products, carbon dioxide being the other main oxidation product.
James J De Voss - One of the best experts on this subject based on the ideXlab platform.
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cytochrome p450 cyp199a4 from rhodopseudomonas palustris catalyzes heteroatom dealkylations sulfoxidation and amide and cyclic hemiacetal formation
ACS Catalysis, 2018Co-Authors: T Coleman, James J De Voss, John B. Bruning, Siew Hoon Wong, M N Podgorski, Stephen G BellAbstract:The cytochrome P450 enzymes execute a range of selective oxidative biotransformations across many biological systems. The bacterial enzyme CYP199A4 catalyzes the oxidative demethylation of 4-Methoxybenzoic Acid. The benzoic Acid moiety of the molecule binds in the active site of the enzyme such that the functional group at the para-position is held close to the heme iron. Therefore, CYP199A4 has the potential to catalyze alternative monooxygenase reactions with different para-substituted benzoic Acid substrates such as thioethers and alkylamines. The oxidation of 4-methyl- and 4-ethyl-thiobenzoic Acids by CYP199A4 resulted in sulfur oxidation. 4-Ethylthiobenzoic Acid sulfoxidation and 4-ethylbenzoic Acid hydroxylation by CYP199A4 occurred with high enantioselectivity (>74% enantiomeric excess). By way of contrast, CYP199A4 catalyzed exclusive oxidative N-demethylation over N-oxide formation with 4-methyl- and 4-dimethylaminobenzoic Acids. Unexpectedly acetamide formation by CYP199A4 competes with dealkyla...
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the importance of the benzoic Acid carboxylate moiety for substrate recognition by cyp199a4 from rhodopseudomonas palustris haa2
Biochimica et Biophysica Acta, 2016Co-Authors: T Coleman, Rebecca R Chao, James J De Voss, Stephen G BellAbstract:Abstract Background The cytochrome P450 enzyme CYP199A4 can efficiently demethylate 4-Methoxybenzoic Acid. The substrate is positioned in the enzyme active site with the methoxy group ideally positioned for demethylation. This occurs through interactions of hydrophobic benzene ring with aromatic phenylalanine residues and the charged carboxylate group with polar and basic amino Acids. Methods In vitro substrate binding and kinetic turnover assays coupled with HPLC and GC–MS analysis and whole-cell oxidation turnovers. Results Modification of the carboxylate group to an amide or aldehyde resulted in substrate binding, as judged by the almost total shift of the spin state to the high-spin form, but binding was three orders of magnitude weaker. Changing the carboxylate to phenol alcohol, ketone, ester and nitro groups and boronic, sulfinic and sulfonic Acids resulted in a dramatic reduction in the binding affinity. Even phenylacetic Acids were mediocre substrates for CYP199A4, despite maintaining a carboxylate group. The weaker binding of all of these substrates results in lower levels of turnover activity and product formation compared to 4-Methoxybenzoic Acid. Conclusion Substrate binding to CYP199A4 is tightly regulated by interactions between the 4-Methoxybenzoic Acid and the amino Acids in the active site. The benzoic Acid carboxylate moiety is critical for optimal substrate binding and turnover activity with CYP199A4. General significance An understanding of how the CYP199A4 enzyme has evolved to be highly selective for para -substituted benzoic Acids. This provides valuable insight into how other, as yet structurally uncharacterised, monooxygenase enzymes may bind benzoic Acid substrates.
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CYP199A4 catalyses the efficient demethylation and demethenylation of para-substituted benzoic Acid derivatives
RSC Advances, 2015Co-Authors: T Coleman, Rebecca R Chao, James J De Voss, John B. Bruning, Stephen G BellAbstract:The cytochrome P450 enzyme CYP199A4, from Rhodopseudomonas palustris strain HaA2, can efficiently demethylate 4-Methoxybenzoic Acid via hemiacetal formation and subsequent elimination of formaldehyde. Oxidative demethylation of a methoxy group para to the carboxyl moiety is strongly favoured over reaction at one in the ortho or meta positions. Dimethoxybenzoic Acids containing a para-methoxy group were also efficiently demethylated exclusively at the para position. The presence of additional methoxy substituents reduces the substrate binding affinity and the activity compared to 4-Methoxybenzoic Acid. The addition of the smaller hydroxy group to the ortho or meta positions or of a nitrogen heteroatom in the aromatic ring of the 4-methoxybenzoate skeleton was better tolerated by the enzyme and these analogues were also readily demethylated. There was no evidence of methylenedioxy ring formation with 3-hydroxy-4-Methoxybenzoic Acid, an activity which is observed with certain plant CYP enzymes with analogous substrates. CYP199A4 is also able to deprotect the methylenedioxy group of 3,4-(methylenedioxy)benzoic Acid to yield 3,4-dihydroxybenzoic Acid and formic Acid. This study defines the substrate range of CYP199A4 and reveals that substrates without a para substituent are not oxidised with any significant activity. Therefore para-substituted benzoic Acids are ideal substrate scaffolds for the CYP199A4 enzyme and will aid in the design of optimised probes to investigate the mechanism of this class of enzymes. They also allow an assessment of the potential of CYP199A4 for synthetic biocatalytic processes involving selective oxidative demethylation or demethenylation.
