The Experts below are selected from a list of 30558 Experts worldwide ranked by ideXlab platform
Dianna J Bowles - One of the best experts on this subject based on the ideXlab platform.
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the activity of arabidopsisglycosyltransferases toward salicylic acid 4 hydroxybenzoic acid and other Benzoates
Journal of Biological Chemistry, 2002Co-Authors: Engkiat Lim, Doucet Charlotte Juliette, Luisa Elias, Dawn Worrall, Steven P Spencer, Joe Ross, Dianna J BowlesAbstract:Benzoates are a class of natural products containing compounds of industrial and strategic importance. In plants, the compounds exist in free form and as conjugates to a wide range of other metabolites such as glucose, which can be attached to the carboxyl group or to specific hydroxyl groups on the benzene ring. These glucosylation reactions have been studied for many years, but to date only one gene encoding a Benzoate glucosyltransferase has been cloned. A phylogenetic analysis of sequences in the Arabidopsis genome revealed a large multigene family of putative glycosyltransferases containing a consensus sequence typically found in enzymes transferring glucose to small molecular weight compounds such as secondary metabolites. Ninety of these sequences have now been expressed as recombinant proteins in Escherichia coli, and their in vitro catalytic activities toward Benzoates have been analyzed. The data show that only 14 proteins display activity toward 2-hydroxybenzoic acid, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid. Of these, only two enzymes are active toward 2-hydroxybenzoic acid, suggesting they are the Arabidopsis salicylic acid glucosyltransferases. All of the enzymes forming glucose esters with the metabolites were located in Group L of the phylogenetic tree, whereas those forming O-glucosides were dispersed among five different groups. Catalytic activities were observed toward glucosylation of the 2-, 3-, or 4-hydroxyl group on the ring. To further explore their regioselectivity, the 14 enzymes were analyzed against benzoic acid, 3-hydroxybenzoic acid, 2,3-, 2,4-, 2,5-, and 2,6-dihydroxybenzoic acid. The data showed that glycosylation of specific sites could be positively or negatively influenced by the presence of additional hydroxyl groups on the ring. This study provides new tools for biotransformation reactions in vitro and a basis for engineering Benzoate metabolism in plants.
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the activity of arabidopsis glycosyltransferases toward salicylic acid 4 hydroxybenzoic acid and other Benzoates
Journal of Biological Chemistry, 2002Co-Authors: Engkiat Lim, Doucet Charlotte Juliette, Luisa Elias, Dawn Worrall, Steven P Spencer, Joe Ross, Dianna J BowlesAbstract:Benzoates are a class of natural products containing compounds of industrial and strategic importance. In plants, the compounds exist in free form and as conjugates to a wide range of other metabolites such as glucose, which can be attached to the carboxyl group or to specific hydroxyl groups on the benzene ring. These glucosylation reactions have been studied for many years, but to date only one gene encoding a Benzoate glucosyltransferase has been cloned. A phylogenetic analysis of sequences in the Arabidopsis genome revealed a large multigene family of putative glycosyltransferases containing a consensus sequence typically found in enzymes transferring glucose to small molecular weight compounds such as secondary metabolites. Ninety of these sequences have now been expressed as recombinant proteins in Escherichia coli, and their in vitro catalytic activities toward Benzoates have been analyzed. The data show that only 14 proteins display activity toward 2-hydroxybenzoic acid, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid. Of these, only two enzymes are active toward 2-hydroxybenzoic acid, suggesting they are the Arabidopsis salicylic acid glucosyltransferases. All of the enzymes forming glucose esters with the metabolites were located in Group L of the phylogenetic tree, whereas those forming O-glucosides were dispersed among five different groups. Catalytic activities were observed toward glucosylation of the 2-, 3-, or 4-hydroxyl group on the ring. To further explore their regioselectivity, the 14 enzymes were analyzed against benzoic acid, 3-hydroxybenzoic acid, 2,3-, 2,4-, 2,5-, and 2,6-dihydroxybenzoic acid. The data showed that glycosylation of specific sites could be positively or negatively influenced by the presence of additional hydroxyl groups on the ring. This study provides new tools for biotransformation reactions in vitro and a basis for engineering Benzoate metabolism in plants.
Junichi Hasegawa - One of the best experts on this subject based on the ideXlab platform.
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inhibitory effects of cucurbitane glycosides and other triterpenoids from the fruit of momordica grosvenori on epstein barr virus early antigen induced by tumor promoter 12 o tetradecanoylphorbol 13 acetate
Journal of Agricultural and Food Chemistry, 2002Co-Authors: Motohiko Ukiya, Teruo Mukainaka, Harukuni Tokuda, Toshihiro Akihisa, Yumiko Kimura, Masakazu Toriumi, Norihiro Banno, Junichi HasegawaAbstract:Two new triterpene Benzoates, 5-dehydrokarounidiol diBenzoate (1) and karounidiol diBenzoate (2), and two new triterpene glycosides, 5α,6α-epoxymogroside IE1 (8) and 11-oxomogroside A1 (9), along with 15 known triterpenoids (one triterpene Benzoate, 3; three triterpene mono-ols, 4−6; one triterpene aglycon, 7; and 10 triterpene glycosides, 10−19), were isolated from the ethanol extract of the fruit of Momordica grosvenori. The structures of 1, 2, 8, and 9 were determined on the basis of spectroscopic and chemical methods. Among the known triterpene glycosides, mogroside I E1 (12) was a new naturally occurring compound. Eighteen triterpenoids (2−19) and 11-oxomogrol (20), a hydrolysis product of 9, were evaluated with respect to their inhibitory effects on the induction of Epstein−Barr virus early antigen (EBV-EA) by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells, which is known to be a primary screening test for antitumor promoters. All of the compounds tested showed potent inhibitory effects on...
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inhibitory effects of cucurbitane glycosides and other triterpenoids from the fruit of momordica grosvenori on epstein barr virus early antigen induced by tumor promoter 12 o tetradecanoylphorbol 13 acetate
Journal of Agricultural and Food Chemistry, 2002Co-Authors: Motohiko Ukiya, Teruo Mukainaka, Harukuni Tokuda, Toshihiro Akihisa, Yumiko Kimura, Masakazu Toriumi, Norihiro Banno, Junichi HasegawaAbstract:Two new triterpene Benzoates, 5-dehydrokarounidiol diBenzoate (1) and karounidiol diBenzoate (2), and two new triterpene glycosides, 5alpha,6alpha-epoxymogroside IE(1) (8) and 11-oxomogroside A(1) (9), along with 15 known triterpenoids (one triterpene Benzoate, 3; three triterpene mono-ols, 4-6; one triterpene aglycon, 7; and 10 triterpene glycosides, 10-19), were isolated from the ethanol extract of the fruit of Momordica grosvenori. The structures of 1, 2, 8, and 9 were determined on the basis of spectroscopic and chemical methods. Among the known triterpene glycosides, mogroside I E(1) (12) was a new naturally occurring compound. Eighteen triterpenoids (2-19) and 11-oxomogrol (20), a hydrolysis product of 9, were evaluated with respect to their inhibitory effects on the induction of Epstein-Barr virus early antigen (EBV-EA) by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells, which is known to be a primary screening test for antitumor promoters. All of the compounds tested showed potent inhibitory effects on EBV-EA induction (70-100% inhibition at 1 x 10(3) mol ratio/TPA).
James M Mayer - One of the best experts on this subject based on the ideXlab platform.
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c h oxidation in fluorenyl Benzoates does not proceed through a stepwise pathway revisiting asynchronous proton coupled electron transfer
Chemical Science, 2021Co-Authors: Scott Coste, Anna C Brezny, Brian Koronkiewicz, James M MayerAbstract:2-Fluorenyl Benzoates were recently shown to undergo C–H bond oxidation through intramolecular proton transfer coupled with electron transfer to an external oxidant. Kinetic analysis revealed unusual rate-driving force relationships. Our analysis indicated a mechanism of multi-site concerted proton–electron transfer (MS-CPET) for all of these reactions. More recently, an alternative interpretation of the kinetic data was proposed to explain the unusual rate-driving force relationships, invoking a crossover from CPET to a stepwise mechanism with an initial intramolecular proton transfer (PT) (Costentin, Saveant, Chem. Sci., 2020, 11, 1006). Here, we show that this proposed alternative pathway is untenable based on prior and new experimental assessments of the intramolecular PT equilibrium constant and rates. Measurement of the fluorenyl 9-C–H pKa, H/D exchange experiments, and kinetic modelling with COPASI eliminate the possibility of a stepwise mechanism for C–H oxidation in the fluorenyl Benzoate series. Implications for asynchronous (imbalanced) MS-CPET mechanisms are discussed with respect to classical Marcus theory and the quantum-mechanical treatment of concerted proton–electron transfer.
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c h oxidation in fluorenyl Benzoates does not proceed through a stepwise pathway revisiting asynchronous proton coupled electron transfer
ChemRxiv, 2021Co-Authors: Scott Coste, Anna C Brezny, Brian Koronkiewicz, James M MayerAbstract:2-fluorenyl Benzoates were recently shown to undergo C–H bond oxidation through intramolecular proton transfer coupled with electron transfer to an external oxidant. Kinetic analysis revealed unusual rate-driving force relationships and indicated a mechanism of multi-site concerted proton-electron transfer (MS-CPET) for all reactions. More recently, an alternative interpretation of the data was proposed to explain the rate-driving force relationships, invoking a crossover from CPET to a stepwise mechanism with an initial intramolecular proton transfer (PT) (Costentin, Saveant, Chem. Sci., 2020, 11, 1006). Here, we show that this proposed alternative pathway is untenable based on new experimental assessments of the intramolecular PT equilibrium constant and rates. Measurement of the fluorenyl 9-C–H pKa, H/D exchange experiments, and kinetic modelling eliminate the possibility of a stepwise mechanism for C–H oxidation in the fluorenyl Benzoate series. Implications for asynchronous MS-CPET mechanisms are discussed with respect to classical Marcus theory and the quantum-mechanical treatment of CPET.
Engkiat Lim - One of the best experts on this subject based on the ideXlab platform.
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the activity of arabidopsisglycosyltransferases toward salicylic acid 4 hydroxybenzoic acid and other Benzoates
Journal of Biological Chemistry, 2002Co-Authors: Engkiat Lim, Doucet Charlotte Juliette, Luisa Elias, Dawn Worrall, Steven P Spencer, Joe Ross, Dianna J BowlesAbstract:Benzoates are a class of natural products containing compounds of industrial and strategic importance. In plants, the compounds exist in free form and as conjugates to a wide range of other metabolites such as glucose, which can be attached to the carboxyl group or to specific hydroxyl groups on the benzene ring. These glucosylation reactions have been studied for many years, but to date only one gene encoding a Benzoate glucosyltransferase has been cloned. A phylogenetic analysis of sequences in the Arabidopsis genome revealed a large multigene family of putative glycosyltransferases containing a consensus sequence typically found in enzymes transferring glucose to small molecular weight compounds such as secondary metabolites. Ninety of these sequences have now been expressed as recombinant proteins in Escherichia coli, and their in vitro catalytic activities toward Benzoates have been analyzed. The data show that only 14 proteins display activity toward 2-hydroxybenzoic acid, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid. Of these, only two enzymes are active toward 2-hydroxybenzoic acid, suggesting they are the Arabidopsis salicylic acid glucosyltransferases. All of the enzymes forming glucose esters with the metabolites were located in Group L of the phylogenetic tree, whereas those forming O-glucosides were dispersed among five different groups. Catalytic activities were observed toward glucosylation of the 2-, 3-, or 4-hydroxyl group on the ring. To further explore their regioselectivity, the 14 enzymes were analyzed against benzoic acid, 3-hydroxybenzoic acid, 2,3-, 2,4-, 2,5-, and 2,6-dihydroxybenzoic acid. The data showed that glycosylation of specific sites could be positively or negatively influenced by the presence of additional hydroxyl groups on the ring. This study provides new tools for biotransformation reactions in vitro and a basis for engineering Benzoate metabolism in plants.
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the activity of arabidopsis glycosyltransferases toward salicylic acid 4 hydroxybenzoic acid and other Benzoates
Journal of Biological Chemistry, 2002Co-Authors: Engkiat Lim, Doucet Charlotte Juliette, Luisa Elias, Dawn Worrall, Steven P Spencer, Joe Ross, Dianna J BowlesAbstract:Benzoates are a class of natural products containing compounds of industrial and strategic importance. In plants, the compounds exist in free form and as conjugates to a wide range of other metabolites such as glucose, which can be attached to the carboxyl group or to specific hydroxyl groups on the benzene ring. These glucosylation reactions have been studied for many years, but to date only one gene encoding a Benzoate glucosyltransferase has been cloned. A phylogenetic analysis of sequences in the Arabidopsis genome revealed a large multigene family of putative glycosyltransferases containing a consensus sequence typically found in enzymes transferring glucose to small molecular weight compounds such as secondary metabolites. Ninety of these sequences have now been expressed as recombinant proteins in Escherichia coli, and their in vitro catalytic activities toward Benzoates have been analyzed. The data show that only 14 proteins display activity toward 2-hydroxybenzoic acid, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid. Of these, only two enzymes are active toward 2-hydroxybenzoic acid, suggesting they are the Arabidopsis salicylic acid glucosyltransferases. All of the enzymes forming glucose esters with the metabolites were located in Group L of the phylogenetic tree, whereas those forming O-glucosides were dispersed among five different groups. Catalytic activities were observed toward glucosylation of the 2-, 3-, or 4-hydroxyl group on the ring. To further explore their regioselectivity, the 14 enzymes were analyzed against benzoic acid, 3-hydroxybenzoic acid, 2,3-, 2,4-, 2,5-, and 2,6-dihydroxybenzoic acid. The data showed that glycosylation of specific sites could be positively or negatively influenced by the presence of additional hydroxyl groups on the ring. This study provides new tools for biotransformation reactions in vitro and a basis for engineering Benzoate metabolism in plants.
Motohiko Ukiya - One of the best experts on this subject based on the ideXlab platform.
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inhibitory effects of cucurbitane glycosides and other triterpenoids from the fruit of momordica grosvenori on epstein barr virus early antigen induced by tumor promoter 12 o tetradecanoylphorbol 13 acetate
Journal of Agricultural and Food Chemistry, 2002Co-Authors: Motohiko Ukiya, Teruo Mukainaka, Harukuni Tokuda, Toshihiro Akihisa, Yumiko Kimura, Masakazu Toriumi, Norihiro Banno, Junichi HasegawaAbstract:Two new triterpene Benzoates, 5-dehydrokarounidiol diBenzoate (1) and karounidiol diBenzoate (2), and two new triterpene glycosides, 5α,6α-epoxymogroside IE1 (8) and 11-oxomogroside A1 (9), along with 15 known triterpenoids (one triterpene Benzoate, 3; three triterpene mono-ols, 4−6; one triterpene aglycon, 7; and 10 triterpene glycosides, 10−19), were isolated from the ethanol extract of the fruit of Momordica grosvenori. The structures of 1, 2, 8, and 9 were determined on the basis of spectroscopic and chemical methods. Among the known triterpene glycosides, mogroside I E1 (12) was a new naturally occurring compound. Eighteen triterpenoids (2−19) and 11-oxomogrol (20), a hydrolysis product of 9, were evaluated with respect to their inhibitory effects on the induction of Epstein−Barr virus early antigen (EBV-EA) by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells, which is known to be a primary screening test for antitumor promoters. All of the compounds tested showed potent inhibitory effects on...
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inhibitory effects of cucurbitane glycosides and other triterpenoids from the fruit of momordica grosvenori on epstein barr virus early antigen induced by tumor promoter 12 o tetradecanoylphorbol 13 acetate
Journal of Agricultural and Food Chemistry, 2002Co-Authors: Motohiko Ukiya, Teruo Mukainaka, Harukuni Tokuda, Toshihiro Akihisa, Yumiko Kimura, Masakazu Toriumi, Norihiro Banno, Junichi HasegawaAbstract:Two new triterpene Benzoates, 5-dehydrokarounidiol diBenzoate (1) and karounidiol diBenzoate (2), and two new triterpene glycosides, 5alpha,6alpha-epoxymogroside IE(1) (8) and 11-oxomogroside A(1) (9), along with 15 known triterpenoids (one triterpene Benzoate, 3; three triterpene mono-ols, 4-6; one triterpene aglycon, 7; and 10 triterpene glycosides, 10-19), were isolated from the ethanol extract of the fruit of Momordica grosvenori. The structures of 1, 2, 8, and 9 were determined on the basis of spectroscopic and chemical methods. Among the known triterpene glycosides, mogroside I E(1) (12) was a new naturally occurring compound. Eighteen triterpenoids (2-19) and 11-oxomogrol (20), a hydrolysis product of 9, were evaluated with respect to their inhibitory effects on the induction of Epstein-Barr virus early antigen (EBV-EA) by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells, which is known to be a primary screening test for antitumor promoters. All of the compounds tested showed potent inhibitory effects on EBV-EA induction (70-100% inhibition at 1 x 10(3) mol ratio/TPA).