20 research outputs found

    Non-host class II ribonucleotide reductase in Thermus viruses: sequence adaptation and host interaction

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    Ribonucleotide reductases (RNR) are essential enzymes for all known life forms. Their current taxonomic distribution suggests extensive horizontal gene transfer e.g., by processes involving viruses. To improve our understanding of the underlying processes, we characterized a monomeric class II RNR (NrdJm) enzyme from a Thermus virus, a subclass not present in any sequenced Thermus spp. genome. Phylogenetic analysis revealed a distant origin of the nrdJm gene with the most closely related sequences found in mesophiles or moderate thermophiles from the Firmicutes phylum. GC-content, codon usage and the ratio of coding to non-coding substitutions (dN/dS) suggest extensive adaptation of the gene in the virus in terms of nucleotide composition and amino acid sequence. The NrdJm enzyme is a monomeric B12-dependent RNR with nucleoside triphosphate specificity. It exhibits a temperature optimum at 60–70 °C, which is in the range of the growth optimum of Thermus spp. Experiments in combination with the Thermus thermophilus thioredoxin system show that the enzyme is able to retrieve electrons from the host NADPH pool via host thioredoxin and thioredoxin reductases. This is different from other characterized viral RNRs such as T4 phage RNR, where a viral thioredoxin is present. We hence show that the monomeric class II RNR, present in Thermus viruses, was likely transferred from an organism phylogenetically distant from the one they were isolated from, and adapted to the new host in genetic signature and amino acids sequence

    The ABC transporter DerAB of <i>Lactobacillus casei</i> mediates resistance against insect-derived defensins

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    Bce-like systems mediate resistance against antimicrobial peptides in Firmicutes bacteria. Lactobacillus casei BL23 encodes an “orphan” ABC transporter that, based on homology to BceAB-like systems, was proposed to contribute to antimicrobial peptide resistance. A mutant lacking the permease subunit was tested for sensitivity against a collection of peptides derived from bacteria, fungi, insects, and humans. Our results show that the transporter specifically conferred resistance against insect-derived cysteine-stabilized αÎČ defensins, and it was therefore renamed DerAB for defensin resistance ABC transporter. Surprisingly, cells lacking DerAB showed a marked increase in resistance against the lantibiotic nisin. This could be explained by significantly increased expression of the antimicrobial peptide resistance determinants regulated by the Bce-like systems PsdRSAB (formerly module 09) and ApsRSAB (formerly module 12). Bacterial two-hybrid studies in Escherichia coli showed that DerB could interact with proteins of the sensory complex in the Psd resistance system. We therefore propose that interaction of DerAB with this complex in the cell creates signaling interference and reduces the cell’s potential to mount an effective nisin resistance response. In the absence of DerB, this negative interference is relieved, leading to the observed hyperactivation of the Psd module and thus increased resistance to nisin. Our results unravel the function of a previously uncharacterized Bce-like orphan resistance transporter with pleiotropic biological effects on the cell.This work was financially supported by DFG grant MA2837/3-2 (to T.M.) and by funds from the former Spanish Ministry of Science and Innovation and FEDER (grant AGL2010-15679) and the Generalitat Valenciana (grant ACOMP2012/137) (to M.Z.). A.R.-G. thanks the Federation of European Microbiological Societies for research grant FEMS-RG-2014-0067. Q.Z. is financially supported by a stipend from the China Scholarship Council (CSC).Peer reviewe

    Enzyme-catalysed regio- and enantioselective preparative scale synthesis of (S)-2-hydroxy alkanones

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    α-Hydroxy alkanones were synthesised with high enantiomeric purity by stereoselective enzyme-catalysed diketone reduction. Both diketone reduction and cofactor regeneration were accomplished with purified carbonyl reductase from Candida parapsilosis (CPCR2). The reaction products were isolated by column chromatography and analysed by chiral GC measurements, 1H-NMR spectroscopy and determination of optical rotations. Preparative-scale biotransformations yielded 350–600 mg of pure aliphatic α-hydroxy ketones including the difficult to obtain (S)-2-hydroxypentane-3-one. For all the products good enantiomeric excesses in the range of 89–93% were achieved

    A Novel One-Pot Enzyme Cascade for the Biosynthesis of Cladribine Triphosphate

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    Cladribine triphosphate is the active compound of the anti-cancer and multiple sclerosis drug Mavenclad (cladribine). Biosynthesis of such non-natural deoxyribonucleotides is challenging but important in order to study the pharmaceutical modes of action. In this study, we developed a novel one-pot enzyme cascade for the biosynthesis of cladribine triphosphate, starting with the nucleobase 2Cl-adenine and the generic co-substrate phosphoribosyl pyrophosphate. The cascade is comprised of the three enzymes, namely, adenine phosphoribosyltransferase (APT), polyphosphate kinase (PPK), and ribonucleotide reductase (RNR). APT catalyzes the binding of the nucleobase to the ribose moiety, followed by two consecutive phosphorylation reactions by PPK. The formed nucleoside triphosphate is reduced to the final product 2Cl-deoxyadenonsine triphosphate (cladribine triphosphate) by the RNR. The cascade is feasible, showing comparative product concentrations and yields to existing enzyme cascades for nucleotide biosynthesis. While this study is limited to the biosynthesis of cladribine triphosphate, the design of the cascade offers the potential to extend its application to other important deoxyribonucleotides

    Development of a Thioredoxin-Based Cofactor Regeneration System for NADPH-Dependent Oxidoreductases

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    Nicotinamide cofactor-dependent oxidoreductases have become a valuable tool for the synthesis of high value chiral compounds. The feasibility of biocatalytic processes involving these enzymes stands and falls with the efficiency of the regeneration of cofactors. In this study, we describe a novel NADPH regeneration method based on the natural thioredoxin electron delivery system. Thioredoxin 1 (Trx1) and thioredoxin reductase (TR) from Thermus thermophilus were characterized for the dithiol-dependent reduction of NADP+, revealing good catalytic activities and a particularly remarkable thermostability. The TR/Trx1 system was then coupled with two representative NADPH-dependent oxidoreductases, alcohol dehydrogenase and cyclohexanone monooxygenase. Reaction conditions for both systems were optimized for reaction yield and selectivity. The results demonstrate the feasibility of the TR/Trx1-system for its application as NADPH regeneration system

    Advanced Insights into Catalytic and Structural Features of the Zinc-Dependent Alcohol Dehydrogenase from Thauera aromatica

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    The asymmetric reduction of ketones to chiral hydroxyl compounds by alcohol dehydrogenases (ADHs) is an established strategy for the provision of valuable precursors for fine chemicals and pharmaceutics. However, most ADHs favor linear aliphatic and aromatic carbonyl compounds, and suitable biocatalysts with preference for cyclic ketones and diketones are still scarce. Among the few candidates, the alcohol dehydrogenase from Thauera aromatica (ThaADH) stands out with a high activity for the reduction of the cyclic α-diketone 1,2-cyclohexanedione to the corresponding α-hydroxy ketone. This study elucidates catalytic and structural features of the enzyme. ThaADH showed a remarkable thermal and pH stability as well as stability in the presence of polar solvents. A thorough description of the substrate scope combined with the resolution and description of the crystal structure, demonstrated a strong preference of ThaADH for cyclic α-substituted cyclohexanones, and indicated structural determinants responsible for the unique substrate acceptance

    Advanced Insights into Catalytic and Structural Features of the Zinc-Dependent Alcohol Dehydrogenase from Thauera aromatica

    No full text
    The asymmetric reduction of ketones to chiral hydroxyl compounds by alcohol dehydrogenases (ADHs) is an established strategy for the provision of valuable precursors for fine chemicals and pharmaceutics. However, most ADHs favor linear aliphatic and aromatic carbonyl compounds, and suitable biocatalysts with preference for cyclic ketones and diketones are still scarce. Among the few candidates, the alcohol dehydrogenase from Thauera aromatica (ThaADH) stands out with a high activity for the reduction of the cyclic α-diketone 1,2-cyclohexanedione to the corresponding α-hydroxy ketone. This study elucidates catalytic and structural features of the enzyme. ThaADH showed a remarkable thermal and pH stability as well as stability in the presence of polar solvents. A thorough description of the substrate scope combined with the resolution and description of the crystal structure, demonstrated a strong preference of ThaADH for cyclic α-substituted cyclohexanones, and indicated structural determinants responsible for the unique substrate acceptance

    Magnetic Multi-Enzymatic System for Cladribine Manufacturing

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    Enzyme-mediated processes have proven to be a valuable and sustainable alternative to traditional chemical methods. In this regard, the use of multi-enzymatic systems enables the realization of complex synthetic schemes, while also introducing a number of additional advantages, including the conversion of reversible reactions into irreversible processes, the partial or complete elimination of product inhibition problems, and the minimization of undesirable by-products. In addition, the immobilization of biocatalysts on magnetic supports allows for easy reusability and streamlines the downstream process. Herein we have developed a cascade system for cladribine synthesis based on the sequential action of two magnetic biocatalysts. For that purpose, purine 2â€Č-deoxyribosyltransferase from Leishmania mexicana (LmPDT) and Escherichia coli hypoxanthine phosphoribosyltransferase (EcHPRT) were immobilized onto Ni2+-prechelated magnetic microspheres (MagReSynÂźNTA). Among the resulting derivatives, MLmPDT3 (activity: 11,935 IU/gsupport, 63% retained activity, operational conditions: 40 °C and pH 5–7) and MEcHPRT3 (12,840 IU/gsupport, 45% retained activity, operational conditions: pH 5–8 and 40–60 °C) emerge as optimal catalysts for further synthetic application. Moreover, the MLmPDT3/MEcHPRT3 system was biochemically characterized and successfully applied to the one-pot synthesis of cladribine under various conditions. This methodology not only displayed a 1.67-fold improvement in cladribine synthesis (compared to MLmPDT3), but it also implied a practically complete transformation of the undesired by-product into a high-added-value product (90% conversion of Hyp into IMP). Finally, MLmPDT3/MEcHPRT3 was reused for 16 cycles, which displayed a 75% retained activity

    The calculated enthalpies of the nine pyrazole anions, cations, and radicals: a comparison with experiment

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    Enthalpies of 12 pyrazole species including neutral, anions, cations, and radicals have been calculated at the G3B3 level. The main conclusions are: (i) there are ten equilibria between species of which six have been measured experimentally and the agreement is excellent; (ii) two structures, cyclic and chain, have been found for the pyrazolium-radical 8 that are able to explain the electrochemistry of pyrazolium salts; (iii) the aromaticity, calculated as the NICS indexes, is related to the unexpected stability of the pyrazole anion 3. © 2006 Elsevier Ltd. All rights reserved.Peer Reviewe
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