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Regeneration System (regeneration + system)

Distribution by Scientific Domains

Chemistry	80%

Selected Abstracts

A New Regeneration System for Oxidized Nicotinamide Cofactors

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009
Seda Aksu
Abstract A novel regeneration system for oxidized nicotinamide cofactors (NAD+ and NADP+) is presented. By combining 2,2,-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS)-catalyzed oxidation of NAD(P)H with laccase-catalyzed utilization of molecular oxygen as terminal oxidant, a simple chemo-enzymatic NAD(P)+ regeneration method is achieved. Thus, the advantages of both worlds, chemical oxidation of reduced nicotinamide cofactors and laccase-catalyzed utilization of oxygen from air are combined in a simple and generally applicable new approach for biooxidation catalysis. This new application of the well-known laccase-mediator system (LMS) is successfully used to promote alcohol dehydrogenase-catalyzed oxidation reactions of primary and secondary alcohols. Already under non-optimized conditions, high turnover numbers of >300 and >16000 were obtained for the nicotinamide cofactor and ABTS, respectively. In this communication, we present the proof-of-principle and initial characterization of the proposed new regeneration system. [source]

Optimization of culture conditions for plant regeneration of Panicum spp. through somatic embryogenesis

GRASSLAND SCIENCE, Issue 1 2010
Mi-Suk Seo
Abstract We developed a rapid and efficient shoot regeneration system for Panicum spp. by adjusting the regeneration medium and studying the responses of different genotypes and the influence of explant types (mature seed, immature embryo and shoot apex). We used Panicum meyerianum (Nees) and Panicum longijubatum (Stapf) which were shown to perform well, to select the optimal medium for shoot regeneration. The highest frequency of shoot regeneration was obtained on Murashige and Skoog medium supplemented with 30 g L,1 maltose and 1 mg L,1 N-phenyl-N,-[(1,2,3-thidiazol-5-yl) urea]. The callus formed green spots after 1 week of culture and showed primary green shoots after 2 weeks. In this system, the calli derived from mature seed of nine Panicum genotypes showed large variation in shoot regeneration ability: from 0 to 69.9% in the frequency of shoot formation and from 0 to 8.4 in the number of shoots per callus. Guineagrass (Panicum maximum Jacq.) showed no ability and switchgrass (Panicum virgatum L.) showed low ability to regenerate from mature seed-derived calli; however, both were able to be regenerated from immature embryos and calli derived from shoot apices. We developed an efficient protocol for high shoot regeneration of various Panicum genotypes which provides a foundation for efficient tissue culture and genetic improvement of Panicum. [source]

A New Regeneration System for Oxidized Nicotinamide Cofactors

Towards Preparative Scale Steroid Hydroxylation with Cytochrome P450 Monooxygenase CYP106A2

CHEMBIOCHEM, Issue 5 2010
Daniela Zehentgruber Dr.
Abstract Cytochrome P450 monooxygenases are of outstanding interest for the synthesis of pharmaceuticals and fine chemicals, due to their ability to hydroxylate CH bonds mainly in a stereo- and regioselective manner. CYP106A2 from Bacillus megaterium ATCC 13368, one of only a few known bacterial steroid hydroxylases, enables the oxidation of 3-keto-4-ene steroids mainly at position 15. We expressed this enzyme together with the electron-transfer partners bovine adrenodoxin and adrenodoxin reductase in Escherichia coli. Additionally an enzyme-coupled cofactor regeneration system was implemented by expressing alcohol dehydrogenase from Lactobacillus brevis. By studying the conversion of progesterone and testosterone, the bottlenecks of these P450-catalyzed hydroxylations were identified. Substrate transport into the cell and substrate solubility turned out to be crucial for the overall performance. Based on these investigations we developed a new concept for CYP106A2-catalyzed steroid hydroxylations by which the productivity of progesterone and testosterone conversion could be increased up to 18-fold to yield an absolute productivity up to 5.5 g,L,1,d,1. Product extraction with absorber resins allowed the recovery of quantitative amounts of 15,-OH-progesterone and 15,-OH-testosterone and also the reuse of the biocatalyst. [source]

One-Pot Multienzymatic Synthesis of 12-Ketoursodeoxycholic Acid: Subtle Cofactor Specificities Rule the Reaction Equilibria of Five Biocatalysts Working in a Row

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009
Daniela Monti
Abstract The hydroxysteroid dehydrogenases (HSDHs)-catalyzed one-pot enzymatic synthesis of 12-ketoursodeoxycholic acid (3,,7,-dihydroxy-12-oxo-5,-cholanoic acid), a key intermediate for the synthesis of ursodeoxycholic acid, from cholic acid has been investigated. This goal has been achieved by alternating oxidative and reductive steps in a one-pot system employing HSDHs with different cofactor specificity, namely NADH-dependent HSDHs in the oxidative step and an NADPH-dependent 7,-HSDH in the reductive one. Coupled in situ regeneration systems have been exploited not only to allow the use of catalytic amounts of the cofactors, but also to provide the necessary driving force to opposite reactions (i.e., oxidation and reduction) acting on different sites of the substrate molecule. Biocatalysts suitable for the set-up of this process have been selected and their kinetic behaviour in respect of the reactions of interest has been evaluated. Finally, the process has been studied employing the enzymes both in free and compartmentalized form. [source]