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31.
Chareonthiphakorn N Wititsuwannakul D Golan-Goldhirsh A Wititsuwannakul R 《Phytochemistry》2002,61(2):123-128
NAD(P)H quinone reductase [NAD(P)H-QR] present in the latex of Hevea brasiliensis Müll.-Arg. (Euphorbiaceae) was purified to homogeniety from the B-serum fraction obtained by freeze-thawing of the bottom fraction of ultracentrifuged fresh latex. The purification protocol involved acetone fractionation, heat treatment, ion exchange chromatography and affinity chromatography. The M(r) determined by SDS-PAGE for the protein subunit was 21 kDa, and the molecular mass of the native enzyme estimated by gel filtration was 83 kDa, indicating that the native enzyme is a homotetramer. The enzyme showed pH stability over a range of 6 to at least 10 (with an optimum at pH 8) and thermal stability up to 80 degrees C. High NAD(P)H-QR activity (70%) was still retained after 10 h of preincubation at 80 degrees C. A comparable substrate specificity for this enzyme was observed among menadione, p-benzoquinone, juglone, and plumbagin, with only duroquinone generating a lower activity. Positive correlations between latex NAD(P)H-QR activity and rubber yield per tapping [fresh latex (r=0.89, P<0.01), dry rubber (r=0.81, P<0.01)] together with flow time (r=0.85, P<0.01) indicated that enzyme activity could possibly be used as a marker to predict the yield potential of selected clones. 相似文献
32.
Wu X Kobori H Orita I Zhang C Imanaka T Xing XH Fukui T 《Biotechnology and bioengineering》2012,109(1):53-62
A novel thermostable NAD(P)H oxidase from the hyperthermophilic archaeon Thermococcus kodakarensis KOD1 (TkNOX) catalyzes oxidation of NADH and NADPH with oxygen from atmospheric air as an electron acceptor. Although the optimal temperature of TkNOX is >90°C, it also shows activity at 30°C. This enzyme was used for the regeneration of both NADP(+) and NAD(+) in alcohol dehydrogenase (ADH)-catalyzed enantioselective oxidation of racemic 1-phenylethanol. NADP(+) regeneration at 30°C was performed by TkNOX coupled with (R)-specific ADH from Lactobacillus kefir, resulting in successful acquisition of optically pure (S)-1-phenylethanol. The use of TkNOX with moderately thermostable (S)-specific ADH from Rhodococcus erythropolis enabled us to operate the enantioselective bioconversion accompanying NAD(+) regeneration at high temperatures. Optically pure (R)-1-phenylethanol was successfully obtained by this system after a shorter reaction time at 45-60°C than that at 30°C, demonstrating an advantage of the combination of thermostable enzymes. The ability of TkNOX to oxidize both NADH and NADPH with remarkable thermostability renders this enzyme a versatile tool for regeneration of the oxidized nicotinamide cofactors without the need for extra substrates other than dissolved oxygen from air. 相似文献
33.
Peter Stäheli Peter Kradolfer Peter Niederberger Ralf Hütter 《Archives of microbiology》1981,129(2):146-149
The effect of the tryptophan analogue 4-methyltryptophan in Saccharomyces cerevisiae has been investigated. 4-Methyltryptophan inhibits the aminoacylation of tryptophan specific transfer ribonucleic acid (tRNATrp). The mode of inhibition is competitive and the analogue is not charged onto tRNATrp. Thus 4-methyltryptophan application depletes the cells from charged tRNATrp. As a consequence cell growth and protein synthesis are strongly reduced. 4-Methyltryptophan is degraded efficiently in culture media inoculated with the wild type strain; the effects of 4-methyltryptophan were therefore found to be transient. 相似文献
34.
35.
The crystal structure of seabream antiquitin in complex with the cofactor NAD(+) was solved at 2.8A resolution. The mouth of the substrate-binding pocket is guarded by two conserved residues, Glu120 and Arg300. To test the role of these two residues, we have prepared the two mutants E120A and R300A. Our model and kinetics data suggest that antiquitin's specificity towards the substrate alpha-aminoadipic semialdehyde is contributed mainly by Glu120 which interacts with the alpha-amino group of the substrate. On the other hand, Arg300 does not have any specific interaction with the alpha-carboxylate group of the substrate, but is important in maintaining the active site conformation. 相似文献
36.
Ahmed O.H. El-Nezhawy Majed Alrobaian Ahmed Khames Mohamed F. El-Badawy Sayed F. Abdelwahab 《Bioorganic & medicinal chemistry》2019,27(7):1263-1273
A general strategy towards total synthesis of (-)-codonopsinine, (-)-codonopsine and codonopsinine analogues has been developed from (D)-tartaric acid via the intermediate (3S,4R)-1-methyl-2-oxo-5-(2,2,2-trichloroacetamido)pyrrolidinediacetate (7). α-amidoalkylation studies of 7 with electron rich benzene derivative 8a-g as C-nucleophiles afforded (aryl derivatives) 9a-g. The target compounds 1, 2 and 13c-g were readily obtained from 10a-g via Grignard addition to the homochiral lactam which was produced by deoxygenation using Lewis-acid followed by deacetylation. The synthesized compounds were loaded onto solid lipid nanoparticle formulations (SLNs) prepared by hot emulsification-ultrasonication technique using Compritol as solid lipid and Pluronic f68 as surfactant. SLNs were fully evaluated and the permeation of synthesized compound from SLNs was assayed against non-formulated compounds through dialysis membranes using Franz cell. The data indicated good physical characteristics of the prepared SLNs, sustaining of release profiles and significant improvement of permeation ability when compared to the non-formulated compounds. The antibacterial and antifungal activities of 1, 2 and 13c-g were determined by disc diffusion and microbroth dilution method to determine the minimum inhibitory concentrations (MIC) against seven microorganisms (Staphyloccus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Acinetobacter baumannii and Candida albicans). The most active compounds against the Gram positive S. aureus were 1, 13C, 13d, and 13g. Also, 13c, 13d, and 13e had antibacterial activity but not 13f against some Gram negative organisms (E. coli, and P. mirabilis). MIC concentrations against P. aeruginosa, and K. pneumoniae were?≥512?μg/ml, while that against A. baumannii was?≥128?μg/ml except for nanoformulae of 13e and 13f that were 16 and 64?μg/ml, respectively. No antifungal activity against Candida albicans was recorded for all compounds and their nanoformulae (MIC?>?1024?μg/ml). SLNs were found to decrease the MIC values for some of the compounds with no effect on the antifungal activity. In conclusion, we demonstrated a novel, straight-forward and economical procedure for the total synthesis of (-)-codonopsinine 1, (-)-codonopsine 2 and codonopsinine analogues 13c-g from simple and commercially available starting materials; d-tartaric acid; with antimicrobial activities against Gram positive and Gram-negative organisms that were improved by SLNs formulations. 相似文献
37.
Markussen MD Heiberg AC Fredholm M Kristensen M 《Journal of biochemical and molecular toxicology》2007,21(6):373-381
The present study characterizes the anticoagulant resistance mechanism in a Danish bromadiolone-resistant strain of Norway rats (Rattus norvegicus), with a Y139C VKORC1 mutation. We compared liver expression of the VKORC1 gene, which encodes a protein of the vitamin K 2,3-epoxide reductase complex, the NQO1 gene, which encodes a NAD(P)H quinone dehydrogenase and the Calumenin gene between bromadiolone-resistant and anticoagulant-susceptible rats upon saline and bromadiolone administration. Additionally, we established the effect of bromadiolone on the gene expression in the resistant and susceptible phenotype. Bromadiolone had no effect on VKORC1 and NQO1 expression in resistant rats, but induced significantly Calumenin expression in the susceptible rats. Calumenin expression was similar between the resistant and the susceptible rats upon saline administration but twofold lower in resistant rats after bromadiolone treatment. These results indicate that Danish bromadiolone resistance does not involve an overexpression of calumenin. Independent of the treatment, we observed a low VKORC1 expression in resistant rats, which in conjugation with the Y139C polymorphism most likely explains the low VKOR activity and the enhanced need for vitamin K observed in Danish resistant rats. Furthermore the bromadiolone resistance was found to be associated with a low expression of the NQO1 gene. 相似文献
38.
S. I. Selivanov A. Yu. Solov’ev S. N. Morozkina A. G. Shavva 《Russian Journal of Bioorganic Chemistry》2007,33(3):302-309
All the signals in the 1H and 13C NMR spectra of some analogues of 7α-methyl-8α-and 6-oxa-8α-steroid estrogens were completely assigned. Considering the values of nuclear Overhauser effect and vicinal coupling constants, these steroids were shown to exhibit a fast, on the NMR time scale, conformational equilibrium arising due to the inversion of ring B. The conformer populations were obtained from a comparison of the experimental and theoretical values of the dihedral angles and the interproton distances. This conformational equilibrium was shown to depend on the nature of atom in position 6: for the 7α-methyl-6-oxa-8α analogues of the steroid estrogens, the population of the conformer with the pseudoaxial orientation of the 7α-methyl group was observed to be decreased compared with the 7α-methyl-8α analogue. 相似文献
39.
Martina Bancirova 《Luminescence》2011,26(6):685-688
Reactive oxygen species (ROS) are presently thought to play important role in an increasing number of the physiological and pathological processes in living organisms. Various chemiluminescent (CL) compounds have been studied in order to find suitable and specific probes for the detection of particular ROS species. The CL of luminol is known to be non‐specific and can be induced by various oxidants. Two Cypridina luciferin analogues, CLA and MCLA, have been used for the detection of ROS in vivo. CLAs are thought to emit light only when reacting with superoxide and singlet oxygen. It is possible to distinguish the particular ROS by using a specific quencher or scavenger, e.g. superoxide dismutase (SOD) or sodium azide (NaN3). The CL reactions of luminol (3‐aminophthalhydrazide), CLA [2‐methyl‐6‐phenyl‐3,7‐dihydroimidazo(1,2α) pyrazin‐3‐one] and MCLA [2‐methyl‐6‐(p‐methoxyphenyl)‐3,7‐dihydroimidazo(1,2α) pyrazin‐3‐one] were studied in three hydrogen peroxide decomposition systems (H2O2–HRP; H2O2–CuSO4; and H2O2–NaOCl). The measurements were carried out in phosphate buffer, pH 7.4, at 25 °C, using a luminometer (Fluoroskan Ascent FL and Sirius C). NaN3 was used as the specific quencher of singlet oxygen. The results demonstrate that the proclaimed specifity of the CL of Cypridina luciferin analogues towards singlet oxygen has to be discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
40.
Brenda S. Speer Ludmila Chistoserdova Mary E. Lidstrom 《FEMS microbiology letters》1994,121(3):349-355
Abstract A fragment of Methylobacter marinus A45 DNA has been cloned and sequenced, and an open reading frame has been identified that could code for a 46-kDa polypeptide. Comparison of the deduced amino acid sequence of the polypeptide against the protein data bank has revealed strong similarity with a number of alcohol dehydrogenases, with highest similarity towards class III alcohol dehydrogenases, which recently have been shown to be identical to glutathione-dependent formaldehyde dehydrogenases. We were unable to measure appreciable levels of NAD(P)-dependent formaldehyde dehydrogenases or alcohol dehydrogenase activities using aldehydes or primary or secondary alcohols in cell-free extracts from batch cultures of M. marinus A45. However, formaldehyde dehydrogenases activity was detected on zymograms. Our data suggest that, although NAD(P)-linked formaldehyde dehydrogenase or alcohol dehydrogenase activities are undetectable in cell-free extracts of most methylotrophs employing the ribulose monophosphate pathway for formaldehyde assimilation and dissimilation, the gene encoding formaldehyde dehydrogenase is present in M. marinus A45 and may be present in more of these organisms as well. 相似文献