2-O-Acetyl-3,4,5,6-tetra-O-benzyl-d-myo-inosityl diphenylphosphate: A new useful intermediate to inositol phosphate and phospholipids.

Inositol phosphates and inositol phospholipids are ubiquitous in biochemistry and play a central role in cell signaling and regulation events. For this reason, their synthesis has attracted widespread interest. This paper describes the preparation of a new optically active inositol phosphate derivative, 2-O-acetyl-3,4,5,6-tetra-O-benzyl-d-myo-inosityl diphenylphosphate (6), and its characterization by spectroscopic methods. Compound (6) represents a useful intermediate for the preparation of inositol phosphate and phospholipids, in particular of glycerophosphoinositol (GPI), a natural anti-inflammatory agent.

An Enzymatic Flow-Based Preparative Route to Vidarabine.

The bi-enzymatic synthesis of the antiviral drug vidarabine (arabinosyladenine, ara-A), catalyzed by uridine phosphorylase from Clostridium perfringens (CpUP) and a purine nucleoside phosphorylase from Aeromonas hydrophila (AhPNP), was re-designed under continuous-flow conditions. Glyoxyl-agarose and EziGTM1 (Opal) were used as immobilization carriers for carrying out this preparative biotransformation. Upon setting-up reaction parameters (substrate concentration and molar ratio, temperature, pressure, residence time), 1 g of vidarabine was obtained in 55% isolated yield and >99% purity by simply running the flow reactor for 1 week and then collecting (by filtration) the nucleoside precipitated out of the exiting flow. Taking into account the substrate specificity of CpUP and AhPNP, the results obtained pave the way to the use of the CpUP/AhPNP-based bioreactor for the preparation of other purine nucleosides.

Phytosterol and γ-Oryzanol Conjugates: Synthesis and Evaluation of their Antioxidant, Antiproliferative, and Anticholesterol Activities.

Fifteen new multifunctional conjugates were designed and synthesized by chemically linking the steroidal framework of natural occurring γ-oryzanol and γ-oryzanol-derived phytosterols to a wide range of bioactive natural compounds (fatty acids, phenolic acids, amino acids, lipoic acid, retinoic acid, curcumin, and resveratrol). Starting from γ-oryzanol, which is the main component of rice bran oil, this study was aimed at assessing if the conjugation strategy might enhance some γ-oryzanol bioactivities. The antioxidant activity was evaluated through three different mechanisms, namely, DPPH-scavenging activity, metal-chelating activity, and ß-carotene-bleaching inhibition. Measurement of the in vitro cell growth inhibitory effects on three different human cancer cellular lines was also carried out, and the potential hypocholesterolemic effect was studied. Compounds 10 and 15 displayed an improved antioxidant activity, with respect to that of γ-oryzanol. Compounds 2, 6, and 12 exerted an antiproliferative activity in the low micromolar range against HeLa and DAOY cells (GI50 < 10 µM). As for the claimed hypocholesterolemic effect of γ-oryzanol, none of the synthesized compounds inhibited the 3-hydroxy-3-methylglutaryl-coenzyme A reductase, a key enzyme in cholesterol biosynthesis.

Assessment of immobilized PGA orientation via the LC-MS analysis of tryptic digests of the wild type and its 3K-PGA mutant assists in the rational design of a high-performance biocatalyst.

The mutant penicillin G acylase (PGA) 3K-PGA contains three additional Lys residues on the surface opposite the active site. This protein was designed to selectively drive its immobilization on aldehyde supports. We describe here a modified bottom-up proteomic method to assess the orientation of the immobilized wild-type and mutant proteins to verify our hypothesis of a driven immobilization induced by the mutations introduced. Tryptic digestion of the immobilized enzymes followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of released peptides was performed. This protocol generated peptides from the most accessible surface areas of the immobilized protein, thus not directly bound to the solid support, providing direct evidence of the areas involved in the linkage to the solid matrix. The results obtained suggest that 72 % of the wild-type PGA is immobilized on aldehyde agarose mainly through the Lys residues on the same side of the active site, whereas 3K-PGA reacted with the same support preferentially through the additional Lys residues introduced by mutation on the opposite side. This demonstrates that the active site of the 3K-PGA faces mostly (63 %) toward the reaction medium, resulting in significantly improved accessibility to the substrates. This finding is supported by the catalytic properties of the immobilized biocatalysts. The two immobilized preparations were tested in the synthesis of mandelyl-7-aminocephalosporanic acid (mandelyl-7-ACA) by N-acylation of the ß-lactam nucleus (7-aminocephalosporanic acid) with mandelic acid methyl ester: upon immobilization, the synthetic properties of wild-type PGA strongly decreased, whereas those of 3K-PGA were unaffected. Furthermore, the activity of 3K-PGA was not influenced by the physicochemical nature of the support used for immobilization (glyoxyl agarose or aldehyde Sepabeads) unlike that of wild-type PGA, whose active site is close to the matrix. The results obtained from the analytical characterization correlate well with those obtained by investigation of the synthetic properties of the immobilized enzymes both in the synthesis of mandelyl-7-ACA and in the preparative synthesis of cefazolin. This work highlights the effect exerted by site-directed mutagenesis on the orientation of PGA upon immobilization on solid matrices and suggests how protein engineering tools can be exploited in a synergistic fashion to rationally develop efficient biocatalysts.

Modulation of the microenvironment surrounding the active site of penicillin G acylase immobilized on acrylic carriers improves the enzymatic synthesis of cephalosporins.

The catalytic properties of penicillin G acylase (PGA) from Escherichia coli in kinetically controlled synthesis of ß-lactam antibiotics are negatively affected upon immobilization on hydrophobic acrylic carriers. Two strategies have been here pursued to improve the synthetic performance of PGA immobilized on epoxy-activated acrylic carriers. First, an aldehyde-based spacer was inserted on the carrier surface by glutaraldehyde activation (immobilization yield = 50%). The resulting 3-fold higher synthesis/hydrolysis ratio (vs/vh1 = 9.7 ± 0.7 and 10.9 ± 0.7 for Eupergit® C and Sepabeads® EC-EP, respectively) with respect to the unmodified support (vs/vh1 = 3.3 ± 0.4) was ascribed to a facilitated diffusion of substrates and products as a result of the increased distance between the enzyme and the carrier surface. A second series of catalysts was prepared by direct immobilization of PGA on epoxy-activated acrylic carriers (Eupergit® C), followed by quenching of oxiranes not involved in the binding with the protein with different nucleophiles (amino acids, amines, amino alcohols, thiols and amino thiols). In most cases, this derivatization increased the synthesis/hydrolysis ratio with respect to the non derivatized carrier. Particularly, post-immobilization treatment with cysteine resulted in about 2.5-fold higher vs/vh1 compared to the untreated biocatalyst, although the immobilization yield decreased from 70% (untreated Eupergit® C) to 20%. Glutaraldehyde- and cysteine-treated Eupergit® C catalyzed the synthesis of cefazolin in 88% (±0.9) and 87% (±1.6) conversion, respectively, whereas untreated Eupergit® C afforded this antibiotic in 79% (±1.2) conversion.

From Lactose to Alkyl Galactoside Fatty Acid Esters as Non-Ionic Biosurfactants: A Two-Step Enzymatic Approach to Cheese Whey Valorization.

A library of alkyl galactosides was synthesized to provide the "polar head" of sugar fatty acid esters to be tested as non-ionic surfactants. The enzymatic transglycosylation of lactose resulted in alkyl ß-D-galactopyranosides, whereas the Fischer glycosylation of galactose afforded isomeric mixtures of α- and ß-galactopyranosides and α- and ß-galactofuranosides. n-Butyl galactosides from either routes were enzymatically esterified with palmitic acid, used as the fatty acid "tail" of the surfactant, giving the corresponding n-butyl 6-O-palmitoyl-galactosides. Measurements of interfacial tension and emulsifying properties of n-butyl 6-O-palmitoyl-galactosides revealed that the esters of galactopyranosides are superior to those of galactofuranosides, and that the enantiopure n-butyl 6-O-palmitoyl-ß-D-galactoside, prepared by the fully enzymatic route, leads to the most stable emulsion. These results pave the way to the use of lactose-rich cheese whey as raw material for the obtainment of bio-based surfactants.

l-Theanine Goes Greener: A Highly Efficient Bioprocess Catalyzed by the Immobilized γ-Glutamyl Transferase from Bacillus subtilis.

l-Theanine (l-Th) was synthesized by simply mixing the reactants (l-glutamine and ethylamine in water) at 25 °C and Bacillus subtilis γ-glutamyl transferase (BsGGT) covalently immobilized on glyoxyl-agarose according to a methodology previously reported by our research group; neither buffers, nor other additives were needed. Ratio of l-glutamine (donor) to ethylamine (acceptor), pH, enzymatic units (IU), and reaction time were optimized (molar ratio of donor/acceptor=1 : 8, pH 11.6, 1 IU mL-1 , 6 h), furnishing l-Th in 93 % isolated yield (485 mg, 32.3 g L-1 ) and high purity (99 %), after a simple filtration of the immobilized biocatalyst, distillation of the volatiles (unreacted ethylamine) and direct lyophilization. Immobilized BsGGT was re-used (four reaction cycles) with 100 % activity retention. This enzymatic synthesis represents a straightforward, fast, high-yielding, and easily scalable approach to l-Th preparation, besides having a favorable green chemistry metrics.

From Batch to Continuous Flow Bioprocessing: Use of an Immobilized γ-Glutamyl Transferase from B. subtilis for the Synthesis of Biologically Active Peptide Derivatives.

γ-Glutamyl-peptides are frequently endowed with biological activities. In this work, "kokumi peptides" such as γ-glutamyl-methionine (1) and γ-glutamyl-(S)-allyl-cysteine (2), as well as the neuroprotective γ-glutamyl-taurine (3) and the antioxidant ophthalmic acid (4), were synthesized through an enzymatic transpeptidation reaction catalyzed by the γ-glutamyl transferase from Bacillus subtilis (BsGGT) using glutamine as the γ-glutamyl donor. BsGGT was covalently immobilized on glyoxyl-agarose resulting in high protein immobilization yield and activity recovery (>95%). Compounds 1-4 were obtained in moderate yields (19-40%, 5-10 g/L) with a variable purity depending on the presence of the main byproduct (γ-glutamyl-glutamine, 0-16%). To achieve process intensification and better control of side reactions, the synthesis of 2 was moved from batch to continuous flow. The specific productivity was 1.5 times higher than that in batch synthesis (13.7 µmol/min*g), but it was not accompanied by a paralleled improvement of the impurity profile.

Preparation, Characterization and In Vitro Stability of a Novel ACE-Inhibitory Peptide from Soybean Protein.

A soy protein isolate was hydrolyzed with Alcalase®, Flavourzyme® and their combination, and the resulting hydrolysates (A, F and A + F) were ultrafiltered and analyzed through SDS-PAGE. Fractions with MW < 1 kDa were investigated for their ACE-inhibitory activity, and the most active one (A < 1 kDa) was purified by semi-preparative RP-HPLC, affording three further subfractions. NMR analysis and Edman degradation of the most active subfraction (A1) enabled the identification of four putative sequences (ALKPDNR, VVPD, NDRP and NDTP), which were prepared by solid-phase synthesis. The comparison of their ACE-inhibitory activities suggested that the novel peptide NDRP might be the main agent responsible for A1 fraction ACE inhibition (ACE inhibition = 87.75 ± 0.61%; IC50 = 148.28 ± 9.83 µg mL−1). NDRP acts as a non-competitive inhibitor and is stable towards gastrointestinal simulated digestion. The Multiple Reaction Monitoring (MRM) analysis confirmed the presence of NDRP in A < 1 kDa.

Design of epidermal growth factor immobilization on 3D biocompatible scaffolds to promote tissue repair and regeneration.

Exogenous application of human epidermal growth factor (hEGF) stimulates epidermal wound healing. The aim of this study was to develop bioconjugates based on hEGF mimicking the protein in its native state and thus suitable for tissue engineering applications, in particular for treating skin-related disorders as burns. Ribonuclease A (RNase A) was used to investigate a number of different activated-agarose carriers: cyanogen bromide (CNBr)-activated-agarose and glyoxyl-agarose showed to preserve the appropriate orientation of the protein for receptor binding. EGF was immobilized on these carriers and immobilization yield was evaluated (100% and 12%, respectively). A peptide mapping of unbound protein regions was carried out by LC-MS to take evidence of the residues involved in the immobilization and, consequently, the flexibility and surface accessibility of immobilized EGF. To assess cell proliferative activities, 10, 25, 50, and 100 ng/mL of each immobilized EGF sample were seeded on fibroblast cells and incubated for 24, 48 and 72 h. The immobilized growth factor showed significantly high cell proliferative activity at 50 and 100 ng/mL compared to control and soluble EGF. Although both of the immobilized samples show dose-dependency when seeded with high number of fibroblast cells, CNBr-agarose-EGF showed a significantly high activity at 100 ng/mL and 72 h incubation, compared to glyoxyl-agarose-EGF.

Discovery of a Novel Inhibitor of Human Purine Nucleoside Phosphorylase by a Simple Hydrophilic Interaction Liquid Chromatography Enzymatic Assay.

Human purine nucleoside phosphorylase (HsPNP) belongs to the purine salvage pathway of nucleic acids. Genetic deficiency of this enzyme triggers apoptosis of activated T-cells due to the accumulation of deoxyguanosine triphosphate (dGTP). Therefore, potential chemotherapeutic applications of human PNP inhibitors include the treatment of T-cell leukemia, autoimmune diseases and transplant tissue rejection. In this report, we present the discovery of novel HsPNP inhibitors by coupling experimental and computational tools. A simple, inexpensive, direct and non-radioactive enzymatic assay coupled to hydrophilic interaction liquid chromatography and UV detection (LC-UV using HILIC as elution mode) was developed for screening HsPNP inhibitors. Enzymatic activity was assessed by monitoring the phosphorolysis of inosine (Ino) to hypoxanthine (Hpx) by LC-UV. A small library of 6- and 8-substituted nucleosides was synthesized and screened. The inhibition potency of the most promising compound, 8-aminoinosine (4), was quantified through Ki and IC50 determinations. The effect of HsPNP inhibition was also evaluated in vitro through the study of cytotoxicity on human T-cell leukemia cells (CCRF-CEM). Docking studies were also carried out for the most potent compound, allowing further insights into the inhibitor interaction at the HsPNP active site. This study provides both new tools and a new lead for developing novel HsPNP inhibitors.

Characterization and study of the orientation of immobilized enzymes by tryptic digestion and HPLC-MS: design of an efficient catalyst for the synthesis of cephalosporins.

An innovative approach to determine the orientation of penicillin G acylase (PGA) from Escherichia coli covalently immobilized onto solid supports has been developed. This method is based on tryptic digestion of immobilized PGA followed by HPLC-MS analysis of the released peptides which are supposed to be only those exposed toward the reaction medium and not directly bound to the solid support. To this purpose, PGA was immobilized on Eupergit C (acrylic hydrophobic resin) and glyoxyl-agarose (hydrophilic resin) functionalized with epoxy and aldehyde groups, respectively, both involving the Lys residues of the protein. The peptide maps obtained were analyzed to derive the orientation of immobilized PGA, as the position of the detected Lys gave indication concerning the accessibility of the different areas of the protein. The results indicate that PGA immobilization on both supports involves mainly Lys located near the binding pocket (70%). Some differences in the enzyme orientation on the two supports can be deduced by the presence of different unbound Lys residues in the released peptides, specific to each support (Lys 117alpha for PGA-Eupergit C; Lys 163alpha and Lys 165alpha for PGA-glyoxyl-agarose). These results have been correlated with the data obtained in the kinetically controlled synthesis and indicate that the orientation of PGA on both supports is partially unfavorable, driving the active site near the support surface. This type of orientation of the enzyme enhances the effect of the nature of the support and of the binding chemistry on the catalytic properties. The information obtained indicated the most suitable support and activation strategy to design an immobilized acylase with good synthetic properties for preparative processes. The glyoxyl-Eupergit C support with enhanced porosity synergically combines the mechanical stability and synthetic performances of immobilized PGA and was successfully used in the synthesis of several cephalosporins.

New active site oriented glyoxyl-agarose derivatives of Escherichia coli penicillin G acylase.

BACKGROUND: Immobilized Penicillin G Acylase (PGA) derivatives are biocatalysts that are industrially used for the hydrolysis of Penicillin G by fermentation and for the kinetically controlled synthesis of semi-synthetic beta-lactam antibiotics. One of the most used supports for immobilization is glyoxyl-activated agarose, which binds the protein by reacting through its superficial Lys residues. Since in E. coli PGA Lys are also present near the active site, an immobilization that occurs through these residues may negatively affect the performance of the biocatalyst due to the difficult diffusion of the substrate into the active site. A preferential orientation of the enzyme with the active site far from the support surface would be desirable to avoid this problem. RESULTS: Here we report how it is possible to induce a preferential orientation of the protein during the binding process on aldehyde activated supports. A superficial region of PGA, which is located on the opposite side of the active site, is enriched in its Lys content. The binding of the enzyme onto the support is consequently forced through the Lys rich region, thus leaving the active site fully accessible to the substrate. Different mutants with an increasing number of Lys have been designed and, when active, immobilized onto glyoxyl agarose. The synthetic performances of these new catalysts were compared with those of the immobilized wild-type (wt) PGA. Our results show that, while the synthetic performance of the wt PGA sensitively decreases after immobilization, the Lys enriched mutants have similar performances to the free enzyme even after immobilization. We also report the observations made with other mutants which were unable to undergo a successful maturation process for the production of active enzymes or which resulted toxic for the host cell. CONCLUSION: The desired orientation of immobilized PGA with the active site freely accessible can be obtained by increasing the density of Lys residues on a predetermined region of the enzyme. The newly designed biocatalysts display improved synthetic performances and are able to maintain a similar activity to the free enzymes. Finally, we found that the activity of the immobilized enzyme proportionally improves with the number of introduced Lys.

Development, validation and application of a 96-well enzymatic assay based on LC-ESI-MS/MS quantification for the screening of selective inhibitors against Mycobacterium tuberculosis purine nucleoside phosphorylase.

Mycobacterium tuberculosis (Mtb) purine nucleoside phosphorylase (PNP, EC 2.4.2.1) has been identified as a target for the development of specific inhibitors with potential antimycobacterial activity. We hereby described the development and validation of a new 96-well LC-ESI-MS/MS method to assess the inhibition activity of nucleoside analogues towards MtbPNP and the human PNP (HsPNP). Enzyme activity was determined by monitoring the phosphorolysis of inosine (Ino) to hypoxanthine (Hpx). The enzymatic assay (v = 0.5 mL, enzyme<0.2 µg/well, T = 37 °C) was performed with an overall time of about 15 min/plate for sample processing and 2 min/sample for LC-MS analysis. Validation of the quantification method met the criteria of the CDER guidance of FDA. Kinetic parameters were in agreement with those reported in literature (HsPNP KM = 0.150 ± 0.020 mM vs 0.133 ± 0.015 mM; MtbPNP KM = 0.060 ± 0.009 mM vs 0.040 ± 0.003 mM for Ino), thus demonstrating the reliability of the newly developed enzymatic assay. Preliminary inhibition assays confirmed the effects reported for Acyclovir (Acv) and Formycin A (FA) against HsPNP and MtbPNP. The validated enzymatic assay was applied to the evaluation of a set of 8-halo-, 8-amino-, 8-O-alkyl-substituted purine ribonucleosides synthesized on purpose as potential inhibitors against MtbPNP. The assayed 8-substituted ribonucleosides did not exert a significant inhibitory effect against the tested enzymes up to 1 mM.

1,2-dithiolan-3-ones and derivatives structurally related to leinamycin. Synthesis and biological evaluation.

Leinamycin, an antitumor antibiotic isolated from Streptomyces sp., shows a 1,2-dithiolan-3-one 1-oxide heterocycle that appears to be involved in the biological activity. Several derivatives related to 1,2-dithiolan-3-one 1-oxide have been prepared and their activity as antineoplastic agents have been investigated. The synthesized compounds did not display a significative antitumor or cytotoxic activity in vitro.

Immobilized purine nucleoside phosphorylase from Aeromonas hydrophila as an on-line enzyme reactor for biocatalytic applications.

We described the development of a biochromatographic system which uses a purine nucleoside phosphorylase from Aeromonas hydrophila (AhPNP) for the evaluation of the substrate specificity on nucleoside libraries. AhPNP has been covalently immobilized on a fused silica Open Tubular Capillary (OTC) via Schiff base chemistry. The resulting bioreactor has been characterized by the determination of kinetic constants (Km and Vmax) for a natural substrate (inosine) and then assayed versus all natural purine (deoxy)ribonucleosides and a small library of 6-substituted purine ribosides. Characterization of the bioreactor has been carried out through a bidimensional chromatographic system with the sample on-line transfer from the bioreactor to the analytical column for the separation and quantification of substrate and product. Comparison with the soluble enzyme showed that the AhPNP-based bioreactor is reliable as the same ranking order, with respect to the standard activity assay, was obtained. The stability of the IMER was also assessed and the system was found to be stable up to 60 reactions.

Stabilization of thymidine phosphorylase from Escherichia coli by immobilization and post immobilization techniques.

Homodimeric thymidine phosphorylase from Escherichia coli (TP, E.C. 2.4.2.4) was immobilized on solid support with the aim to have a stable and recyclable biocatalyst for nucleoside synthesis. Immobilization by ionic adsorption on amine-functionalized agarose and Sepabeads(®) resulted in a very high activity recovery (>85%). To prevent undesirable leakage of immobilized enzyme away from the support, the ionic preparations were cross-linked with aldehyde dextran (MW 20 kDa) and the influence of the dextran oxidation degree on the resulting biocatalyst activity was evaluated. Although in all cases the percentage of expressed activity after immobilization drastically decreased (≤ 25%), this procedure allowed to obtain an active catalyst which resulted up to 6-fold and 3-fold more stable than the soluble (non immobilized) enzyme and the just adsorbed (non cross-linked) counterpart, respectively, at pH 10 and 37°C. No release of the enzyme from the support could be observed. Covalent immobilization on aldehyde or epoxy supports was generally detrimental for enzyme activity. Optimal TP preparation, achieved by immobilization onto Sepabeads(®) coated with polyethyleneimine and cross-linked, was successfully used for the one-pot synthesis of 5-fluoro-2'-deoxyuridine starting from 2'-deoxyuridine or thymidine (20mM) and 5-fluorouracil (10mM). In both cases, the reaction proceeded at the same rate (3 µmol min(-1)) affording 62% conversion in 1h.

Enzymatic synthesis of cephalosporins. The immobilized acylase from Arthrobacter viscosus: a new useful biocatalyst.

The acylase from Arthrobacter viscosus was immobilized, studied in the enzymatic synthesis of some cephalosporins by kinetically controlled N-acylation (kcNa) of different cephem nuclei, and compared with the penicillin G acylase (PGA) from Escherichia coli. The reaction outcomes were dependent on the acylase microbial source and on the type of immobilization support. Generally, both enzymes, when immobilized onto hydrophilic resins such as glyoxyl-agarose (activated with aldehyde groups), displayed higher synthetic performances in comparison with hydrophobic acrylic epoxy-supports like Eupergit C. The kcNa of 7-amino cephalosporanic acid catalyzed by A. viscosus immobilized on glyoxyl-agarose afforded a quantitative conversion in 7-[(1-hydroxy-1-phenyl)-acetamido]-3-acetoxymethyl-Delta(3)-cephem-4-carboxylic acid, a useful intermediate for the synthesis of Cefamandole and Cefonicid. Similar results were obtained in the synthesis of these cephalosporins by direct acylation of the corresponding 3'-functionalized nucleus. In these reactions, A. viscosus displayed higher synthetic performances than the PGA from E. coli.

Immobilization and stabilization of recombinant multimeric uridine and purine nucleoside phosphorylases from Bacillus subtilis.

We selected the PnpI/PupG (PNP) with specificity for ribo- and deoxyriboguanosine and ribo- and deoxyriboinosine and the Up/Pdp (UP) with specificity for uridine, thymidine, and deoxyuridine from the purine and pyrimidine salvage pathway of the Gram-positive bacterium Bacillus subtilis. Then, an extensive study of the UP (uridine phosphorylase) and PNP (purine nucleoside phosphorylase) immobilization and stabilization was carried out: optimal UP preparation was achieved by immobilization onto Sepabeads coated with poly(ethyleneimine) and finally cross-linked with aldehyde dextran (UP-Sep-PEI-Dx); optimal immobilized PNP was prepared onto glyoxyl-agarose. Both derivatives were highly stable and active even under drastic experimental conditions (pH 10, 45 degrees C) unlike the free enzymes which were promptly inactivated. The derivatives prepared were successfully used in the synthesis of 2'-deoxyguanosine by enzymatic transglycosylation in aqueous solution between 2'-deoxyuridine and guanine.

New N-alkyl-1,2-dihydro-2-thioxo-3-pyridinecarbothioamides as antituberculous agents with improved pharmacokinetics.

Infections caused by multidrug-resistant Mycobacterium tuberculosis (MT) and non-tuberculous mycobacteria are difficult to treat and, indeed, new therapeutic agents are being sought. As a part of an ongoing research in our laboratories, novel N-alkyl-1,2-dihydro-2-thioxo-3-pyridinecarbothioamides have been synthesized and evaluated against several strains of MT and Mycobacterium avium complex (MAC). The pharmacokinetics and relative bioavailability after intravenous administration of three derivatives have been investigated. Introduction of a hydroxyl or a tertiary amino group in the N-alkyl chain resulted in an improved pharmacokinetic profile without affecting sensitively the antituberculous potency.