Biotechnological synthesis of ribavirin. Effect of ribavirin and its various combinations on the reproduction of Vaccinia virus

The biotechnological method of synthesis of ribavirin, vidarabin, and 6-azauridine by the use of immobilized recombinant enzymatic preparations of nucleoside phosphorylase was improved. The effect of ribavirin and its combinations with the other synthesized nucleosides on the reproduction of Vaccinia virus was studied using cultures of Vero cells. The combination of ribavirin and vidarabin was shown to provide an antiviral effect at lesser concentrations than when these compounds were taken separately. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 6; see also http://www.maik.ru.     

Characterization of Foam- and Emulsion-stabilizing Functions of Enzymatically Modified Proteins with Surfactancy

A papain-catalyzed reaction involving covalent incorporation of l-leucine n-alkyl ester is available for producing an enzymatically modified protein (EMP) with surfactancy [Agric. Biol. Chem., 45, 1621 (1981)]. In the present work we used gelatin as a starting material and incorporated l-leucine n-hexyl ester to produce a whippable EMP and l-leucine n-dodecyl ester to produce an emulsifiable EMP. A foam system formed with the whippable EMP was much stabler than that formed with sodium dodecylsulfate. The emulsifiable EMP also gave a much stabler oil-in-water emulsion than Tween-80 did. The stability of the emulsion formed with EMP was not affected by the presence of NaCl at a very high concentration. The observed foam and emulsion stabilities were well explained by the data for decreased mobility of the involved water protons. These results may indicate that EMP molecules, when arranged at the air/water or oil/water interface, can bind a part of the water to form thick barriers which prevent the air or oil particles from coalescing.     

Labeling of Crithidia fasciculata DNA with [3H]Thymidine

Attempts at continuous labeling of Crithidia fasciculata DNA with [³H]thymidine led to a pulse-chase situation due to a cell-mediated conversion of thymidine to thymine in the medium. The uptake of thymine was slow compared to that of thymidine. Neither the addition of deoxyadenosine nor the sequential addition of several aliquots of [³H]thymidine had an effect on the pattern of labeling.     

A putative hyperglycemic factor from the cerebral ganglia of Otala lactea (Mollusca: Pulmonata)

Mantle tissue pieces from adult Otala lactea continuously synthesized glycogen over a 72-h incubation period. Acid-saline extract of the cerebral ganglia inhibited glycogen synthesis by mantle tissue in vitro. This effect was dose-dependent. The glycogen reduction factor from the cerebral ganglia was heat stable, protease sensitive, and relatively hydrophobic. The cerebral ganglia extract also stimulated mantle glycogen phosphorylase in vitro in a dose-dependent manner. The results suggest the presence of a hyperglycemic factor in the cerebral ganglia of Otala. The molecular weight of this factor, estimated by size-exclusion chromatography, was approximately 10,000. Mammalian glucagon had no significant effect on glycogen synthesis by the mantle pieces. Accepted: 17 January 2000     

Anti-influenza A virus effect of Hypericum perforatum L. extract

To study the antiviral effect of Hypericum perforatum L. extract (HPE) on influenza A virus (IAV) (H₁N₁) in vitro and in vivo. Cytopathic effect (CPE) and neutral red (NR) dye uptake were used to examine the antiviral effect of HPE on Madin Darby Canine Kidney (MDCK) cells which were infected with IAV in vitro. HPE was effective against influenza A virus (IAV) in vitro, with a 50% effective concentration (EC₅₀) of 40 μg/mL. The mean 50% cytotoxic concentration (CC₅₀) in the MDCK used in these experiments was 1.5 mg/mL. Ribavirin was run in parallel with EC₅₀ values of 5.0 μg/mL; the mean CC₅₀ for ribavirin was 520 μg/mL. Oral gavage administrations of HPE or ribavirin to mice infected with the IAV were highly effective in preventing death, slowing the decline of arterial oxygen saturation, inhibiting lung consolidation and reducing lung virus titers. The minimum effective dose of HPE in these studies was 31.25 mg/kg/day, which was administered twice daily for 5 d beginning 4 h prior to virus exposure. Below a dosage of 2000 mg/kg/day, almost all treated mice survived, which suggests that HPE is of low toxicity. Ribavirin’s minimum effective dose was 40 mg/kg/day with the LD50 determined to be 200 mg/kg/day. Delay of the initiation of either HPE or ribavirin therapy, using approximately 1/3 LD₅₀ dose each time, could still be protective as late as 48 h after exposure to the IAV. While both agents appeared to have similar efficacy against IAV infections, HPE was considered to be less toxic and may warrant further evaluation as a possible therapy for influenza. Foundation items: One Hundred Person Project of The Chinese Academy of Sciences (2008-287); The Project of Basic Scientific Research Fund for Central Public-Welfare of Institute of Sciences (BRF070402).     

枯草芽孢杆菌TM903嘌呤核苷磷酸化酶的纯化及酶学性质研究

目的：对枯草芽孢杆菌TM903嘌呤核苷磷酸化酶进行分离纯化及酶学性质研究。方法：经加热、硫酸铵盐析和SephadexG-100凝胶过滤,对枯草芽孢杆菌TM903中的嘌呤核苷磷酸化酶进行分离纯化,并对其酶学性质进行研究。结果：酶的最适反应温度为65℃,最适反应pH值为7．5,在30-50℃时热稳定性较好;K^＋对该酶有激活作用,而Na^＋、ca^＋、Mg^＋、Mn^＋等金属离子对该酶有抑制作用;Km值为2．11mmol／L,Vmax值为0．84mmol／（min·L）。结论：分离纯化了枯草芽孢杆菌TM903嘌呤核苷磷酸化酶,并研究了其酶学性质,为利巴韦林的发酵工艺优化提供了重要的酶学理论基础。     

Reciprocal regulation of glycogen phosphorylase and glycogen synthase by insulin involving phosphatidylinositol-3 kinase and protein phosphatase-1 in HepG2 cells

The effect of insulin on glycogen synthesis and key enzymes of glycogen metabolism, glycogen phosphorylase and glycogen synthase, was studied in HepG2 cells. Insulin stimulated glycogen synthesis 1.83-3.30 fold depending on insulin concentration in the medium. Insulin caused a maximum of 65% decrease in glycogen phosphorylase 'a' and 110% increase in glycogen synthase activities in 5 min. Although significant changes in enzyme activities were observed with as low as 0.5 nM insulin level, the maximum effects were observed with 100 nM insulin. There was a significant inverse correlation between activities of glycogen phosphorylase 'a' and glycogen synthase 'a' (R² = 0.66, p < 0.001). Addition of 30 mM glucose caused a decrease in phosphorylase 'a' activity in the absence of insulin and this effect was additive with insulin up to 10 nM concentration. The inactivation of phosphorylase 'a' by insulin was prevented by wortmannin and rapamycin but not by PD98059. The activation of glycogen synthase by insulin was prevented by wortmannin but not by PD98059 or rapamycin. In fact, PD98059 slightly stimulated glycogen synthase activation by insulin. Under these experimental conditions, insulin decreased glycogen synthase kinase-3 activity by 30-50% and activated more than 4-fold particulate protein phosphatase-1 activity and 1.9-fold protein kinase B activity; changes in all of these enzyme activities were abolished by wortmannin. The inactivation of GSK-3 and activation of PKB by insulin were associated with their phosphorylation and this was also reversed by wortmannin. The addition of protein phosphatase-1 inhibitors, okadaic acid and calyculin A, completely abolished the effects of insulin on both enzymes. These data suggest that stimulation of glycogen synthase by insulin in HepG2 cells is mediated through the PI-3 kinase pathway by activating PKB and PP-1G and inactivating GSK-3. On the other hand, inactivation of phosphorylase by insulin is mediated through the PI-3 kinase pathway involving a rapamycin-sensitive p70^s6k and PP-1G. These experiments demonstrate that insulin regulates glycogen phosphorylase and glycogen synthase through (i) a common signaling pathway at least up to PI-3 kinase and bifurcates downstream and (ii) that PP-1 activity is essential for the effect of insulin.     

Correlation between the Antitumor Activity of Schizophyllan and Its Triple Helix

trans-3-Methylthioacrylamide (3-MTAA-NH₂) was isolated as colorless needles from the culture broth of Streptomyces sioyaensis, a siomycin-producer. This substance is considered to be not only a new metabolite from methionine but also a new substance. The isolation and identification of 3-MTAA-NH₂, as well as the cultural conditions for production, were investigated. A variety of other Streptomyces also produced 3-MTAA-NH₂ from methionine.     

Enzymatic Production of Ribavirin from Pyrimidine Nucleosides by Enterobacter aerogenes AJ 11125

Microorganisms that produce ribavirin(1-β-d-ribofuranosyl-1,2,4-triazole-3-carboxamide; virazole^®) directly from pyrimidine nucleosides and TCA (1,2,4-triazole-3-carboxamide) were screened from our stock cultures. Of the 400 strains tested, 16 were isolated as ribavirin-producers from uridine or cytidine. In particular, Enterobacter aerogenes AJ 11125, Bacillus brevis AJ 1282 and Sarcina lutea AJ 1212 were found to possess potent activities of ribavirin production from them. In the presence of intact cells of Enterobacter aerogenes AJ 11125, which was selected as the best strain, 110.2mm and 67.6 mm ribavirin were produced from uridine and cytidine, respectively, on 96 hr reaction at 60°C. In addition, this strain could also produce ribavirin from guanosine, but could not produce it from orotidine, which is also a pyrimidine nucleoside.     

Radiosensitization by Thymidine Phosphorylase Inhibitor in Thymidine Phosphorylase Negative and Overexpressing Bladder Cancer Cell Lines

TAS-102 (trifluorothymidine [TFT] and thymidine phosphorylase inhibitor [TPI] in a molar ratio of 1:0.5) has activity in 5-fluorouracil resistant colon cancer. TPI is added to increase TFT's bioavailability. TFT has a dual mechanism of action by inhibiting thymidylate synthase and by its incorporation into DNA. Interesting radiosensitizing effects of TPI were recently reported. The aim of our study was to determine whether TP expression would affect radiosensitivity and to characterize the effect of TPI. Two bladder cancer cell lines RT112 (TP negative) and RT112/TP (TP overexpression) were tested for drug sensitivity and radiosensitivity (clonogenic assay), with and without TFT and/or TPI. Expression of γ H2AX was used as marker for DNA damage. RT112 cells were not more sensitive to TFT then RT112/TP cells. TPI alone did not inhibit cell growth of RT112 even at 100 μM, but inhibited that of RT112/TP by 27%. In both RT112 and RT112/TP cells 10 μM TPI did not or slightly affect radiosensitivity, but 100 μM TPI alone enhanced the radiation response (p <.05). TFT alone at 1 μM and in combination with 10 μM TPI did not affect the radiation response of both cell lines. TPI alone induced expression of ?H2AX, which was increased in combination with radiation. In conclusion, TPI enhanced radiosensitivity at high concentrations, independent of TP expression, while TFT and TPI at a low concentration did not affect the radiosensitivity of RT112 and RT112/TP cell lines.     

Optimum Induction of Recombinant Thymidine Phosphorylase and Its Application

Recombinant E. coli pDEOA was constructed and lactose can be used instead of IPTG to induce the expression of thymidine phosphorylase by pDEOA. The use of lactose at concentrations higher than 0.5 mmol/L had an induction effect similar to that of IPTG but resulted in a longer initial induction time and better cell growth. The thymidine phosphorylase induced by lactose was very stable at 50°C. Intact pDEOA cells induced by lactose can be used as a source of thymidine phosphorylase. Under standard reaction conditions, several deoxynucleosides were effectively produced from thymidine.     

Substrate specificity of E. coli uridine phosphorylase. Further evidences of high-syn conformation of the substrate in uridine phosphorolysis

Twenty five uridine analogues have been tested and compared with uridine with respect to their potency to bind to E. coli uridine phosphorylase. The kinetic constants of the phosphorolysis reaction of uridine derivatives modified at 2′-, 3′- and 5′-positions of the sugar moiety and 2-, 4-, 5- and 6-positions of the heterocyclic base were determined. The absence of the 2′- or 5′-hydroxyl group is not crucial for the successful binding and phosphorolysis. On the other hand, the absence of both the 2′- and 5′-hydroxyl groups leads to the loss of substrate binding to the enzyme. The same effect was observed when the 3′-hydroxyl group is absent, thus underlining the key role of this group. Our data shed some light on the mechanism of ribo- and 2′-deoxyribonucleoside discrimination by E. coli uridine phosphorylase and E. coli thymidine phosphorylase. A comparison of the kinetic results obtained in the present study with the available X-ray structures and analysis of hydrogen bonding in the enzyme-substrate complex demonstrates that uridine adopts an unusual high-syn conformation in the active site of uridine phosphorylase.     

The genotoxic and cytotoxic effects of ribavirin in rat bone marrow

The genotoxic and cytotoxic effects of the antiviral drug, ribavirin, was studied in rat bone marrow by employing the micronucleus assay. Ribavirin in doses of 10, 15, 20, 30, 50, 75, 100 and 200 mg/kg, and cyclophosphamide (CP) 40 mg/kg (only for sex-difference study) were injected intraperitoneally. Bone marrow was collected at 24 h and 48 h following the injection. To evaluate the recovery, the bone marrow was also sampled at 72 h from 20, 100 and 200 mg/kg treated rats. The micronucleus assay was conducted according to the standard procedure. Ribavirin elevated the incidence of micronuclei (except 10 mg/kg) in erythrocytes (P<0.01). The micronucleated polychromatic erythrocytes showed the initial steep increase at 15 and 20 mg/kg dose level, then with the gradual increase, possibly due to the limited metabolism and action of higher doses. The incidence of micronucleated normochromatic erythrocytes was not dose dependent. The effect was more at 48 h than 24 h due to prolonged toxicity of the drug or its metabolites, and by 72 h, recovery was observed eventhough the genotoxicity was significant. The PCE% decreased as the dose was increased up to 75 mg/kg, then without much difference between two higher doses. Only 100 mg/kg ribavirin and CP showed more toxicity on male rats. Cytotoxicity was seen due to hindered erythropoiesis or cell destruction. Our findings suggest that ribavirin is genotoxic and cytotoxic agent for rat bone marrow.     

生长调节物质对组培暗紫贝母小鳞茎生长的影响

应用正交实验研究了生长调节物质病毒唑（ｒｉｂａｖｉｒｉｎ）、茉莉酸甲酯（ｊａｓｍｏｎｉｃａｃｉｄｍｅｔｈｙｌｅｓｔｅｒ）、油菜素内酯（ｂｒａｓｉｎｏｌｉｄｅ）、腐殖酸钠（ｓｏｄｉｕｍｈｕｍａｔｅ）对组织培养暗紫贝母（ＦｒｉｔｉｌａｒｉａｕｎｉｂｒａｃｔｅａｔａＨｉｓａｏｅｔＫ．Ｃ．Ｈｓｉａ）小鳞茎生长的影响,发现病毒唑有显著活性。进一步对不同浓度病毒唑的效果进行优化试验,结果表明：病毒唑１０ｍｇ／Ｌ是提高小鳞茎生长率的最适浓度。     

Efficacy of chemotherapy and thermotherapy in elimination of East African cassava mosaic virus from Tanzanian cassava landrace

Cassava mosaic disease is caused by cassava mosaic begomoviruses (CMBs) and can result in crop losses up to 100% in cassava (Manihot esculenta) in Tanzania. We investigated the efficacy of chemotherapy and thermotherapy for elimination of East African cassava mosaic virus (EACMV) of Tanzanian cassava. In vitro plantlets from EACMV‐infected plants obtained from coastal Tanzania were established in the greenhouse. Leaves were sampled from the plants and tested to confirm the presence of EACMV. Plantlets of plants positive for EACMV were initiated in Murashige and Skoog (MS) medium. On the second subculture, they were subjected into chemical treatment in the medium containing salicylic acid (0, 10, 20, 30 and 40 mg/L) and ribavirin (0, 5, 10, 15 and 20 mg/L). In the second experiment, EACMV‐infected plantlets were subjected to temperatures between 35 and 40°C with 28°C as the control. After 42 days of growth, DNA was extracted from plant leaves and PCR amplification was performed using EACMV specific primers. It was found that plant survival decreased with increasing levels of both salicylic acid and ribavirin concentrations. In general, plants treated with salicylic acid exhibited a lower plant survival % than those treated with ribavirin. However, the percentage of virus‐free plants increased with an increase in the concentration of both ribavirin and salicylic acid. The most effective concentrations were 20 mg/L of ribavirin and 30 mg/L of salicylic acid; these resulted in 85.0% and 88.9% virus‐free plantlets, respectively. With regard to thermotherapy, 35°C resulted in 79.5% virus‐free plantlets compared to 69.5% at 40°C. Based on virus elimination, ribavirin at 20 mg/L, salicylic acid 30 mg/L and thermotherapy at 35°C are recommended for production of EACMV free cassava plantlets from infected cassava landraces.     

Stretch affects phenotype and proliferation of vascular smooth muscle cells

The focus of this study was to identify the molecular basis for the hypersensitive response of glycogen phosphorylase activation to epinephrine stimulation in alloxan diabetic-derived cardiomyocytes. Cyclic AMP levels were found not to be significantly different between normal and diabetic-derived cells while cGMP concentrations were found consistently to be significantly lower in diabetic-derived cells than in normal cells. Treatment with cyclic GMP analogues did not affect phosphorylase activation by epinephrine in normal cardiomyocytes whereas, IBMX, a nonselective phosphodiesterase inhibitor, had a significant effect on basal and agonist-stimulated phosphorylase activity in both normal and diabetic-derived cardiomyocytes. Differences in the time course for the rate of decay of phosphorylasea from agonist-stimulated to basal levels were observed between normal and diabetic cells. After 3 h in primary culture, phosphorylasea activity returned to basal levels more quickly in normal than in diabetic-derived cells while after 24 h in culture, the time for phosphorylasea decay was not significantly different between normal and diabetic myocytes and was longer than the 3 h response. After 3 h in primary culture, no significant difference in phosphorylase kinase activity was observed between normal and diabetic-derived cells exposed to epinephrine whereas, after 24 h in culture, phosphorylase kinase activity was significantly decreased in diabetic cells under basal and agonist-stimulated conditions. These data collectively suggest that the hypersensitive response of glycogen phosphorylase to epinephrine stimulation in diabetic-derived cardiomyocytes is not due to a defect present at the level of phosphorylase kinase but may, in part, result from an alteration in cardiac phosphodiesterase activity resulting from diminished intracellular cyclic GMP concentrations.     

High-yielding cascade enzymatic synthesis of 5-methyluridine using a novel combination of nucleoside phosphorylases

Abstract

A novel combination of Bacillus halodurans purine nucleoside phosphorylase (BhPNP1) and Escherichia coli uridine phosphorylase (EcUP) has been applied to a dual-enzyme, sequential, biocatalytic one-pot synthesis of 5-methyluridine from guanosine and thymine. A 5-methyluridine yield of >79% on guanosine was achieved in a reaction slurry at a 53 mM (1.5% w/w) guanosine concentration. 5-Methyluridine is an intermediate in synthetic routes to thymidine and the antiretroviral drugs zidovudine and stavudine.     

Enzymatic Synthesis of α-Anomer-Selective D-Glucosides Using Maltose Phosphorylase

A maltose phosphorylase (EC 2.4.1.8; MPase) showed novel acceptor specificity and transferred the glucosyl moiety of maltose not only to sugars but also to various acceptors having alcoholic OH groups. Salicyl alcohol acted as acceptor for MPase from Enterococcus hirae, and the product, salicyl-O-α-D-glucopyranoside (α-SalGlc) was identified. The yield based on supplied salicyl alcohol was 86% (mol/mol).     

Enzymatic Properties of Recombinant Kojibiose Phosphorylase from Caldicellulosiruptor saccharolyticus ATCC43494

One kojibiose phoshorylase (KP) homolog gene was cloned from Caldicellulosiruptor saccharolyticus ATCC43494. Recombinant KP from C. saccharolyticus (Cs-KP) expressed in Escherichia coli showed highest activity at pH 6.0 at 85 °C, and was stable from pH 3.5 to 10.0 and up to 85 °C for phosphorolysis. Cs-KP showed higher productivity of kojioligosaccharides of DP≧4 than KP from Thermoanaerobacter brockii ATCC35047.     

Mycoplasma in african green monkey kidney cell cultures: Biochemical detection and effects in virus-infected cells

Summary Among a number of techniques for the detection of mycoplasmal contamination in African green monkey kidney (AGMK) cell lines, the assay of uridine phosphorylase activity is unsuitable because of the presence of high levels of endogenous enzymatic activity. A thymidine phosphorylase test, however, based on the chromatographic analysis of radiolabeled thymidine breakdown, turned out to be a simple and sensitive mycoplasma detection method. We found, using the latter technique, that 0.22-μm-filtered virus inocula could still transfer mycoplasma unless treated with diethyl ether. The effect of mycoplasmal contamination on the synthesis of simian virus 40 and adenovirus in AGMK cells was negligible under the conditions used (no depletion of arginine). Incorporation of radioactive thymidine in viral macromolecules, however, was inhibited severely by the presence of mycoplasma. This investigation was supported by a grant from theFonds voor Geneeskundig Wetenschappelijk Onderzoek (No. 20.298). F.V. R. is an Aspirant of the BelgianNationaal Fonds voor Wetenschappelijk Onderzoek.