The Experts below are selected from a list of 99 Experts worldwide ranked by ideXlab platform
Jiri Janata - One of the best experts on this subject based on the ideXlab platform.
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different reaction specificities of f420h2 dependent reductases facilitate pyrrolobenzodiazepines and lincomycin to fit their biological targets
Journal of the American Chemical Society, 2020Co-Authors: Lucie Steiningerova, Zdenek Kamenik, Stanislav Kadlcik, Marek Kuzma, Radek Gazak, Ghader Bashiri, Petr Man, Magdalena Pavlikova, Jiri JanataAbstract:Antitumor pyrrolobenzodiazepines (PBDs), Lincosamide Antibiotics, quorum-sensing molecule hormaomycin, and antimicrobial griselimycin are structurally and functionally diverse groups of actinobacterial metabolites. The common feature of these compounds is the incorporation of l-tyrosine- or l-leucine-derived 4-alkyl-l-proline derivatives (APDs) in their structures. Here, we report that the last reaction in the biosynthetic pathway of APDs, catalyzed by F420H2-dependent Apd6 reductases, contributes to the structural diversity of APD precursors. Specifically, the heterologous overproduction of six Apd6 enzymes demonstrated that Apd6 from the biosynthesis of PBDs and hormaomycin can reduce only an endocyclic imine double bond, whereas Apd6 LmbY and partially GriH from the biosyntheses of lincomycin and griselimycin, respectively, also reduce the more inert exocyclic double bond of the same 4-substituted Δ1-pyrroline-2-carboxylic acid substrate, making LmbY and GriH unusual, if not unique, among reductases. F...
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elucidation of salicylate attachment in celesticetin biosynthesis opens the door to create a library of more efficient hybrid Lincosamide Antibiotics
Chemical Science, 2017Co-Authors: Stanislav Kadlcik, Zdenek Kamenik, D Vasek, M Nedved, Jiri JanataAbstract:Lincosamides, which are produced by streptomycetes, compose a small but clinically important class of Antibiotics. The recent elucidation of the condensation and post-condensation biosynthetic steps of the Lincosamides lincomycin and celesticetin revealed several unexpected reaction mechanisms. Here, we prepared recombinant proteins involved in the celesticetin biosynthetic pathway and used them for in vitro assays that were monitored by LC-MS. Our results elucidate the last biosynthetic step of celesticetin: the attachment of salicylic acid is catalyzed by the Ccb2 acyl-CoA ligase and the Ccb1 acyltransferase. Ccb1 belongs to the WS/DGAT protein family and, in contrast to the characterized members of the family, has unusual substrate specificity. To the best of our knowledge, Ccb1 is the first protein in this family that transfers a benzoyl derivative-CoA conjugate and is the first WS/DGAT protein involved in the biosynthesis of secondary metabolites. Furthermore, we exploited the relaxed substrate specificities of Ccb1 and Ccb2, as well as three additional upstream post-condensation biosynthetic proteins in the celesticetin pathway, and combined the lincomycin and the celesticetin biosynthetic pathways in vitro. In this way, we prepared a library of 150 novel hybrid Lincosamides, including two unnatural chimeras of lincomycin and celesticetin, which were shown to have antibacterial properties more pronounced than clinically used lincomycin. These achievements may be considered a case study in applying knowledge about biosynthetic machinery to assemble a large number of compounds from originally a small group of natural products without the need for chemical synthesis.
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deacetylation of mycothiol derived waste product triggers the last biosynthetic steps of Lincosamide Antibiotics
Chemical Science, 2016Co-Authors: Zdenek Kamenik, Stanislav Kadlcik, Bojana Radojevic, Petra Jiraskova, Marek Kuzma, Radek Gazak, Lucie Najmanova, Jan Kopecky, Jiri JanataAbstract:The immediate post-condensation steps in lincomycin biosynthesis are reminiscent of the mycothiol-dependent detoxification system of actinomycetes. This machinery provides the last proven lincomycin intermediate, a mercapturic acid derivative, which formally represents the ‘waste product’ of the detoxification process. We identified and purified new lincomycin intermediates from the culture broth of deletion mutant strains of Streptomyces lincolnensis and tested these compounds as substrates for proteins putatively involved in lincomycin biosynthesis. The results, based on LC-MS, in-source collision-induced dissociation mass spectrometry and NMR analysis, revealed the final steps of lincomycin biosynthesis, i.e. conversion of the mercapturic acid derivative to lincomycin. Most importantly, we show that deacetylation of the N′-acetyl-S-cysteine residue of the mercapturic acid derivative is required to ‘escape’ the detoxification-like system and proceed towards completion of the biosynthetic pathway. Additionally, our results, supported by L-cysteine-13C3, 15N incorporation experiments, give evidence that a different type of reaction catalysed by the homologous pair of pyridoxal-5′-phosphate-dependent enzymes, LmbF and CcbF, forms the branch point in the biosynthesis of lincomycin and celesticetin, two related Lincosamides.
Timothy Bigwood - One of the best experts on this subject based on the ideXlab platform.
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the development and validation of a multiclass liquid chromatography tandem mass spectrometry lc ms ms procedure for the determination of veterinary drug residues in animal tissue using a quechers quick easy cheap effective rugged and safe approach
Analytica Chimica Acta, 2009Co-Authors: George Stubbings, Timothy BigwoodAbstract:A novel rapid multiresidue/multiclass procedure with liquid chromatography tandem mass spectrometry (LC-MS/MS) detection has been developed to screen for the presence of veterinary drug residues in animal tissues. The method uses a new sample preparation procedure loosely based on QuEChERS (QUick, Easy, CHeap, Effective, Rugged and Safe) methodology. Validation to date has been restricted to chicken muscle and has been performed according to European Commission guidelines [COMMISSION DECISION of 12 August 2002 implementing Council Directive 96/23/EC concerning the performance of analytical methods and the interpretation of results] for nitroimidazoles, sulphonamides, fluoroquinolones, quinolones, ionophores and dinitrocarbanilide. Recent work has shown that the method is also applicable to macrolide and Lincosamide Antibiotics, benzimidazoles, levamisole, avermectins and tranquillisers.
G Font - One of the best experts on this subject based on the ideXlab platform.
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determination of macrolide and Lincosamide Antibiotics by pressurised liquid extraction and liquid chromatography tandem mass spectrometry in meat and milk
Food Control, 2010Co-Authors: Cristina Juan, Juan Carlos Moltó, Jordi Manes, G FontAbstract:Abstract A total of 155 samples, including meat and milk, were analyzed using a method developed for determining five macrolide Antibiotics: tilmicosin (TILM), tylosin (TS), spiramycin (SPM), erythromycin (ERY), and tulathromycin (TULA) and two Lincosamide Antibiotics: pirlimycin (PIRL) and lincomycin (LM). The method was performed by pressurised liquid extraction (PLE) coupled to LC–MS/MS using electrospray ionization in positive ion mode. 2.5 mL of milk or 2.5 g of meat were dispersed in ethylenediaminetetraacetic acid sodium salt 2-hydrate (EDTA) and sea sand. The PLE conditions as: solvent, temperature, pressure, static time, and cell size were optimized. The following analytical parameters were validated according to the guidelines laid down by European Commission Decision 2002/657/EC linearity, specificity, decision limit (CCα), detection capability (CCβ), repeatability, reproducibility, recovery and ruggedness. The frequency of analyzed Antibiotics in milk and meat was 48 and 15%, respectively. Four of positives samples (two of meat and two of milk) were higher than the maximum residues levels (MRLs) established by European Union legislation. The found levels were lower than 78.3 μg/kg in milk and 156 μg/kg in meat. Calculation of the estimated daily intakes (EDIs) from these data showed that contribution of meat and milk to dietary intakes were lower than acceptable daily intakes (ADIs) proposed by JECFA.
George Stubbings - One of the best experts on this subject based on the ideXlab platform.
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the development and validation of a multiclass liquid chromatography tandem mass spectrometry lc ms ms procedure for the determination of veterinary drug residues in animal tissue using a quechers quick easy cheap effective rugged and safe approach
Analytica Chimica Acta, 2009Co-Authors: George Stubbings, Timothy BigwoodAbstract:A novel rapid multiresidue/multiclass procedure with liquid chromatography tandem mass spectrometry (LC-MS/MS) detection has been developed to screen for the presence of veterinary drug residues in animal tissues. The method uses a new sample preparation procedure loosely based on QuEChERS (QUick, Easy, CHeap, Effective, Rugged and Safe) methodology. Validation to date has been restricted to chicken muscle and has been performed according to European Commission guidelines [COMMISSION DECISION of 12 August 2002 implementing Council Directive 96/23/EC concerning the performance of analytical methods and the interpretation of results] for nitroimidazoles, sulphonamides, fluoroquinolones, quinolones, ionophores and dinitrocarbanilide. Recent work has shown that the method is also applicable to macrolide and Lincosamide Antibiotics, benzimidazoles, levamisole, avermectins and tranquillisers.
Cristina Juan - One of the best experts on this subject based on the ideXlab platform.
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determination of macrolide and Lincosamide Antibiotics by pressurised liquid extraction and liquid chromatography tandem mass spectrometry in meat and milk
Food Control, 2010Co-Authors: Cristina Juan, Juan Carlos Moltó, Jordi Manes, G FontAbstract:Abstract A total of 155 samples, including meat and milk, were analyzed using a method developed for determining five macrolide Antibiotics: tilmicosin (TILM), tylosin (TS), spiramycin (SPM), erythromycin (ERY), and tulathromycin (TULA) and two Lincosamide Antibiotics: pirlimycin (PIRL) and lincomycin (LM). The method was performed by pressurised liquid extraction (PLE) coupled to LC–MS/MS using electrospray ionization in positive ion mode. 2.5 mL of milk or 2.5 g of meat were dispersed in ethylenediaminetetraacetic acid sodium salt 2-hydrate (EDTA) and sea sand. The PLE conditions as: solvent, temperature, pressure, static time, and cell size were optimized. The following analytical parameters were validated according to the guidelines laid down by European Commission Decision 2002/657/EC linearity, specificity, decision limit (CCα), detection capability (CCβ), repeatability, reproducibility, recovery and ruggedness. The frequency of analyzed Antibiotics in milk and meat was 48 and 15%, respectively. Four of positives samples (two of meat and two of milk) were higher than the maximum residues levels (MRLs) established by European Union legislation. The found levels were lower than 78.3 μg/kg in milk and 156 μg/kg in meat. Calculation of the estimated daily intakes (EDIs) from these data showed that contribution of meat and milk to dietary intakes were lower than acceptable daily intakes (ADIs) proposed by JECFA.