The Experts below are selected from a list of 14511 Experts worldwide ranked by ideXlab platform
Keith A. Bostian - One of the best experts on this subject based on the ideXlab platform.
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production of l Dihydroxyphenylalanine in escherichia coli with the tyrosine phenol lyase gene cloned from erwinia herbicola
Applied and Environmental Microbiology, 1993Co-Authors: Forrest Foor, N Morin, Keith A. BostianAbstract:The gene (tutA) encoding tyrosine phenol-lyase from Erwinia herbicola was cloned into Escherichia coli, and fusions to the lac and tac promoters were constructed. The enzyme was expressed at high levels in E. coli in the presence of isopropyl-beta-D-thiogalactopyranoside or lactose as an inducer. L-Dihydroxyphenylalanine was synthesized in high yield from catechol, pyruvate, and ammonia by induced cells.
Bong Hyun Sung - One of the best experts on this subject based on the ideXlab platform.
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genetic incorporation of l Dihydroxyphenylalanine dopa biosynthesized by a tyrosine phenol lyase
Chemical Communications, 2018Co-Authors: Bong Hyun SungAbstract:L-Dihydroxyphenylalanine (DOPA) was biosynthesized by a tyrosine-phenol lyase from catechol, pyruvate, and ammonia in Escherichia coli, and the biosynthesized amino acid was directly incorporated into proteins. Three biochemical experiments with mutant proteins containing DOPA confirmed the genetic incorporation of biosynthesized DOPA, and revealed its potential for various biochemical applications.
Shulin Zhao - One of the best experts on this subject based on the ideXlab platform.
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Enantiomeric separation of naphthalene-2,3-dicarboxaldehyde derivatized DL-3,4-Dihydroxyphenylalanine and optical purity analysis of L-3,4-Dihydroxyphenylalanine drug by cyclodextrin-modified micellar electrokinetic chromatography.
Journal of chromatography. A, 2004Co-Authors: Jiangshan Shen, Shulin ZhaoAbstract:A new cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method for the enantiomeric separation of 3,4-Dihydroxyphenylalanine (DOPA), derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) to produce cyanobenzoisoindole (CBI) derivative, has been developed. The unsubstituted alpha-, beta-, gamma-cyclodextrins (CDs) and hydroxypropyl-substituted alpha-, beta-, gamma-CDs, as chiral selector, were examined for the enantiomeric separation of CBI-DL-DOPA. In addition to the concentration of chiral selector, some other experimental factors also have been optimized, such as concentration of borate buffer, content of sodium dodecyl sulphate (SDS), pH of electrolyte and applied voltage. Optimal separation was obtained at pH 8.0, 100 mM borate solution containing 5 mM HP-gamma-CD and 120 mM SDS, as well as 18 kV applied voltage and 25 degrees C capillary temperature. Detection was followed by direct UV absorptiometric measurements at 254 nm. The developed method was employed for optical purity analysis of levodopa drug and allowed the determination of 0.14% D-DOPA in L-3,4-Dihydroxyphenylalanine (levodopa) with well peak identification.
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Enantiomeric separation of naphthalene-2,3-dicarboxaldehyde derivatized DL-3,4-Dihydroxyphenylalanine and optical purity analysis of L-3,4-Dihydroxyphenylalanine drug by cyclodextrin-modified micellar electrokinetic chromatography.
Journal of Chromatography A, 2004Co-Authors: Jiangshan Shen, Shulin ZhaoAbstract:Abstract A new cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method for the enantiomeric separation of 3,4-Dihydroxyphenylalanine (DOPA), derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) to produce cyanobenzoisoindole (CBI) derivative, has been developed. The unsubstituted α-, β-, γ-cyclodextrins (CDs) and hydroxypropyl-substituted α-, β-, γ-CDs, as chiral selector, were examined for the enantiomeric separation of CBI- dl -DOPA. In addition to the concentration of chiral selector, some other experimental factors also have been optimized, such as concentration of borate buffer, content of sodium dodecyl sulphate (SDS), pH of electrolyte and applied voltage. Optimal separation was obtained at pH 8.0, 100 mM borate solution containing 5 mM HP-γ-CD and 120 mM SDS, as well as 18 kV applied voltage and 25 °C capillary temperature. Detection was followed by direct UV absorptiometric measurements at 254 nm. The developed method was employed for optical purity analysis of levodopa drug and allowed the determination of 0.14% d -DOPA in l -3,4-Dihydroxyphenylalanine (levodopa) with well peak identification.
Michele Miranda - One of the best experts on this subject based on the ideXlab platform.
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White truffles, like black ones, are tyrosinase positive
Plant Science, 1996Co-Authors: Michele Miranda, Antonella Bonfigli, Rocchina Porretta, Osvaldo Zarivi, Giovanni Pacioni, Pierpaolo Aimola, Anna Maria RagnelliAbstract:Abstract White truffles, Tuber magnatum Pico and Tuber excavatum Vitt. are both albino tyrosinase positive fungi. Interestingly, while both l -tyrosine-3-monooxygenase and l -3,4-Dihydroxyphenylalanine oxidase activities of T. excavatum Vitt. decrease versus time after decompartmentalization, those of T. magnatum Pico increase. The K m of both species for l -tyrosine are lower than those for l -3,4-Dihydroxyphenylalanine as substrates, while the V max with l -tyrosine are very much lower than those with l -3,4-Dihydroxyphenylalanine. No change of K m versus time was found, only V max change, thus tentatively the inactivation or activation found in T. excavatum Vitt. and T. magnatum Pico tyrosinase activity versus time may be ascribed either to the binding or release of an inhibitor or to the release or binding of an activator, respectively. l -Tyrosine 3-monooxygenase and l -3,4 Dihydroxyphenylalanine oxidase co-localize as shown histochemically.
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Truffle tyrosinase: Properties and activity
Plant Science, 1992Co-Authors: Michele Miranda, Antonella Bonfigli, Osvaldo Zarivi, Giovanni Pacioni, Anna Maria Ragnelli, Dario BottiAbstract:Abstract The present paper investigates the l -3,4-Dihydroxyphenylalanine oxidase (EC 1.14.18.1) and l -tyrosine 3-monooxygenase (EC 1.14.18.1) activities of truffles of the genus Tuber , a highly pigmented group of Ascomycetes. The laccase (EC 1.10.2.1) activity has also been explored in the homogenate supernatants from these mushrooms. The effects of various inhibitors of tyrosinase, of buffer concentration, temperature and pH on the tyrosinase activity of truffle cytosols have been investigated. The K m values of l -3,4-Dihydroxyphenylalanine and l -tyrosine have been calculated and are in the range of those found in other mushrooms (i.e. 0.37 mM and 2.70 mM respectively).The polyacryamide gel electrophoretic pattern of the l -3,4-Dihydroxyphenylalanine oxidase activities of different species of truffles have been obtained. Moreover, the truffle pigment formation and localization have been histochemically investigated and correlated with the reproductive differentiation.
Anna Maria Ragnelli - One of the best experts on this subject based on the ideXlab platform.
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White truffles, like black ones, are tyrosinase positive
Plant Science, 1996Co-Authors: Michele Miranda, Antonella Bonfigli, Rocchina Porretta, Osvaldo Zarivi, Giovanni Pacioni, Pierpaolo Aimola, Anna Maria RagnelliAbstract:Abstract White truffles, Tuber magnatum Pico and Tuber excavatum Vitt. are both albino tyrosinase positive fungi. Interestingly, while both l -tyrosine-3-monooxygenase and l -3,4-Dihydroxyphenylalanine oxidase activities of T. excavatum Vitt. decrease versus time after decompartmentalization, those of T. magnatum Pico increase. The K m of both species for l -tyrosine are lower than those for l -3,4-Dihydroxyphenylalanine as substrates, while the V max with l -tyrosine are very much lower than those with l -3,4-Dihydroxyphenylalanine. No change of K m versus time was found, only V max change, thus tentatively the inactivation or activation found in T. excavatum Vitt. and T. magnatum Pico tyrosinase activity versus time may be ascribed either to the binding or release of an inhibitor or to the release or binding of an activator, respectively. l -Tyrosine 3-monooxygenase and l -3,4 Dihydroxyphenylalanine oxidase co-localize as shown histochemically.
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Truffle tyrosinase: Properties and activity
Plant Science, 1992Co-Authors: Michele Miranda, Antonella Bonfigli, Osvaldo Zarivi, Giovanni Pacioni, Anna Maria Ragnelli, Dario BottiAbstract:Abstract The present paper investigates the l -3,4-Dihydroxyphenylalanine oxidase (EC 1.14.18.1) and l -tyrosine 3-monooxygenase (EC 1.14.18.1) activities of truffles of the genus Tuber , a highly pigmented group of Ascomycetes. The laccase (EC 1.10.2.1) activity has also been explored in the homogenate supernatants from these mushrooms. The effects of various inhibitors of tyrosinase, of buffer concentration, temperature and pH on the tyrosinase activity of truffle cytosols have been investigated. The K m values of l -3,4-Dihydroxyphenylalanine and l -tyrosine have been calculated and are in the range of those found in other mushrooms (i.e. 0.37 mM and 2.70 mM respectively).The polyacryamide gel electrophoretic pattern of the l -3,4-Dihydroxyphenylalanine oxidase activities of different species of truffles have been obtained. Moreover, the truffle pigment formation and localization have been histochemically investigated and correlated with the reproductive differentiation.