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ABSTRACT: Class II fructose 1,6-bisphosphate aldolases (FBA; E.C. 4.1.2.13) comprise one of two families of aldolases. Instead of forming a Schiff-base intermediate using an ε-amino group of a lysine side chain, class II FBAs utilize Zn(II) to stabilize a proposed hydroxyenolate intermediate (HEI) in the reversible cleavage of fructose 1,6-bisphosphate forming glyceraldehyde 3-phosphate and dihydroxyacetone phosphate (DHAP). As class II FBAs has been shown to be essential in pathogenic bacteria, focus has been placed on these enzymes as potential antibacterial targets. Although structural studies on class II FBAs from Mycobacterium tuberculosis (MtFBA), other bacteria and protozoa have been reported, the structure of the active site loop responsible for catalyzing the protonation/deprotonation steps of the reaction for class II FBAs has not yet been observed. We therefore utilized the potent class II FBA inhibitor phosphoglycolohydroxamate (PGH) as a mimic of the HEI/DHAP bound form of the enzyme and determined the X-ray structure of MtFBA-PGH complex to 1.58 Å. Remarkably, we are able to observe well-defined electron density for the previously elusive active site loop of MtFBA trapped in a catalytically competent orientation. Utilization of this structural information plus site-directed mutagenesis and kinetic studies conducted on a series of residues within the active-site loop revealed that E169 facilitates a water mediated deprotonation/protonation step of the MtFBA reaction mechanism. Also, secondary isotope effects on MtFBA and catalytically relevant mutants were used to probe the effect of loop flexibility on catalytic efficiency. Additionally, we also reveal the structure of MtFBA in its holoenzyme form.
Biochemistry 01/2013; · 3.42 Impact Factor
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ABSTRACT: A variety of ammosamide B analogues have been synthesized and evaluated as inhibitors of quinone reductase 2 (QR2). The potencies of the resulting series of QR2 inhibitors range from 4.1 to 25,200 nM. The data provide insight into the structural parameters necessary for QR2 inhibitory activity. The natural product ammosamide B proved to be a potent QR2 inhibitor, and the potencies of the analogues generally decreased as their structures became more distinct from that of ammosamide B. Methylation of the 8-amino group of ammosamide B was an exception, resulting in an increase in quinone reductase 2 inhibitory activity from an IC(50) of 61 nM to IC(50) 4.1 nM.
Journal of Medicinal Chemistry 12/2011; 55(1):367-77. · 4.80 Impact Factor
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ABSTRACT: Upregulation of cytoprotective enzymes by therapeutic agents to prevent damage by reactive oxygen species and xenobiotic electrophiles is a strategy for cancer chemoprevention. The Kelch-like ECH-associated protein 1 (Keap1) and its binding partner, transcription factor NF-E2-related factor-2 (NRF2), are chemoprevention targets because of their role in regulating the antioxidant response element (ARE) in response to oxidative stress and exposure to electrophiles. Modification of the sensor protein Keap1 by electrophiles such as the isothiocyanate sulforaphane can direct Nrf2 accumulation in the nucleus and subsequent ARE activation. Since our previous matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS)-based screening method to discover natural products that modify Keap1 does not detect covalent modification of Keap1 by some highly reversible agents such as sulforaphane, a more sensitive screening assay was developed. In this new assay, electrophiles that have reversibly modified Keap1 can be released, trapped, and detected as β-mercaptoethanol adducts by mass spectrometry. Isoliquiritigenin and sulforaphane, known ARE activators that target Keap1, were used to validate the assay. To determine the ability of the assay to identify electrophiles in complex matrixes that modify Keap1, sulforaphane was spiked into a cocoa extract, and LC-MS/MS using high resolution mass spectrometry with accurate mass measurement was used to identify β-mercaptoethanol adducts of sulforaphane that had been released from Keap1. This screening assay permits identification of potential chemoprevention agents in complex natural product mixtures that reversibly modify Keap1 but cannot be detected using MALDI-TOF MS.
Analytical Biochemistry 10/2011; 421(1):108-14. · 3.00 Impact Factor
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ABSTRACT: Recent reports point to small soluble oligomers, rather than insoluble fibrils, of amyloid β (Aβ), as the primary toxic species in Alzheimer's disease. Previously, we developed a low-throughput assay in yeast that is capable of detecting small Aβ(42) oligomer formation. Specifically, Aβ(42) fused to the functional release factor domain of yeast translational termination factor, Sup35p, formed sodium dodecyl sulfate (SDS)-stable low-n oligomers in living yeast, which impaired release factor activity. As a result, the assay for oligomer formation uses yeast growth to indicate restored release factor activity and presumably reduced oligomer formation. We now describe our translation of this assay into a high-throughput screen (HTS) for anti-oligomeric compounds. By doing so, we also identified two presumptive anti-oligomeric compounds from a sub-library of 12,800 drug-like small molecules. Subsequent biochemical analysis confirmed their anti-oligomeric activity, suggesting that this form of HTS is an efficient, sensitive and cost-effective approach to identify new inhibitors of Aβ(42) oligomerization.
Disease Models and Mechanisms 08/2011; 4(6):822-31. · 4.94 Impact Factor
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ABSTRACT: Bipolar disorder is characterized by a cycle of mania and depression, which affects approximately 5 million people in the United States. Current treatment regimes include the so-called "mood-stabilizing drugs", such as lithium and valproate that are relatively dated drugs with various known side effects. Glycogen synthase kinase-3β (GSK-3β) plays a central role in regulating circadian rhythms, and lithium is known to be a direct inhibitor of GSK-3β. We designed a series of second generation benzofuran-3-yl-(indol-3-yl)maleimides containing a piperidine ring that possess IC₅₀ values in the range of 4 to 680 nM against human GSK-3β. One of these compounds exhibits reasonable kinase selectivity and promising preliminary absorption, distribution, metabolism, and excretion (ADME) data. The administration of this compound at doses of 10 to 25 mg kg⁻¹ resulted in the attenuation of hyperactivity in amphetamine/chlordiazepoxide-induced manic-like mice together with enhancement of prepulse inhibition, similar to the effects found for valproate (400 mg kg⁻¹) and the antipsychotic haloperidol (1 mg kg⁻¹). We also tested this compound in mice carrying a mutation in the central transcriptional activator of molecular rhythms, the CLOCK gene, and found that the same compound attenuates locomotor hyperactivity in response to novelty. This study further demonstrates the use of inhibitors of GSK-3β in the treatment of manic episodes of bipolar/mood disorders, thus further validating GSK-3β as a relevant therapeutic target in the identification of new therapies for bipolar patients.
ChemMedChem 07/2011; 6(9):1593-602. · 3.15 Impact Factor
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ABSTRACT: Quinone reductase 2 (QR2) is one of two members comprising the mammalian quinone reductase family of enzymes responsible for performing FAD mediated reductions of quinone substrates. In contrast to quinone reductase 1 (QR1) which uses NAD(P)H as its co-substrate, QR2 utilizes a rare group of hydride donors, N-methyl or N-ribosyl nicotinamide. Several studies have linked QR2 to the generation of quinone free radicals, several neuronal degenerative diseases, and cancer. QR2 has been also identified as the third melatonin receptor (MT3) through in cellulo and in vitro inhibition of QR2 by traditional MT3 ligands, and through recent X-ray structures of human QR2 (hQR2) in complex with melatonin and 2-iodomelatonin. Several MT3 specific ligands have been developed that exhibit both potent in cellulo inhibition of hQR2 nanomolar, affinity for MT3. The potency of these ligands suggest their use as molecular probes for hQR2. However, no definitive correlation between traditionally obtained MT3 ligand affinity and hQR2 inhibition exists limiting our understanding of how these ligands are accommodated in the hQR2 active site. To obtain a clearer relationship between the structures of developed MT3 ligands and their inhibitory properties, in cellulo and in vitro IC₅₀ values were determined for a representative set of MT3 ligands (MCA-NAT, 2-I-MCANAT, prazosin, S26695, S32797, and S29434). Furthermore, X-ray structures for each of these ligands in complex with hQR2 were determined allowing for a structural evaluation of the binding modes of these ligands in relation to the potency of MT3 ligands.
Protein Science 07/2011; 20(7):1182-95. · 2.80 Impact Factor
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Tamara P Kondratyuk,
Eun-Jung Park,
Laura E Marler,
Soyoun Ahn,
Yang Yuan,
Yongsoo Choi,
Rui Yu,
Richard B van Breemen,
Bin Sun,
Juma Hoshino,
Mark Cushman,
Katherine C Jermihov, Andrew D Mesecar,
Clinton J Grubbs,
John M Pezzuto
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ABSTRACT: Despite scores of investigations, the actual impact of resveratrol (3,5,4'-trihydroxy-trans-stilbene) on human health, as a dietary component or supplement, remains moot. This is due to many factors, such as relatively low potency, pleiotropic mechanisms, and rapid metabolism. Nonetheless, as a promiscuous molecule that interacts with numerous targets, resveratrol can be viewed as a scaffold for designing structural relatives potentially capable of mediating more intense responses with greater mechanistic stringency.
We currently report the synthesis and biological evaluation of 92 stilbene analogs. The compounds were tested with in vitro assays for activation of quinone reductase 1, inhibition of quinone reductase 2, nitric oxide production, aromatase, NFκB, 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase, or cyclooxygenase-1 and -2, quenching of 2,2-diphenyl-1-picrylhydrazyl free radical, interaction with estrogen receptors, and as antiproliferative agents. Several compounds were found to mediate responses with much greater potency than resveratrol; some mediated pleiotropic responses, as is the case with the parent molecule, but others were highly specific or totally inactive. When administered to rats, higher serum concentrations and greater stability was demonstrated with prototype lead molecules.
Owing to structural simplicity, facile syntheses are available for large-scale production. These data support the promise of more advanced development of novel resveratrol derivatives as drug entities.
Molecular Nutrition & Food Research 06/2011; 55(8):1249-65. · 4.30 Impact Factor
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Yongsoo Choi,
Katherine Jermihov,
Sang-Jip Nam,
Megan Sturdy,
Katherine Maloney,
Xi Qiu,
Lucas R Chadwick,
Matthew Main,
Shao-Nong Chen, Andrew D Mesecar,
Norman R Farnsworth,
Guido F Pauli,
William Fenical,
John M Pezzuto,
Richard B van Breemen
Analytical Chemistry 06/2011; 83(11):4325. · 5.86 Impact Factor
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ABSTRACT: Activation of the transcription factor NF-E2-related factor-2 (Nrf2) through modification of Kelch-like ECH-associated protein 1 (Keap1) cysteines, leading to up-regulation of the antioxidant response element (ARE), is an important mechanism of cellular defense against reactive oxygen species and xenobiotic electrophiles. Sulforaphane, occurring in cruciferous vegetables such as broccoli, is a potent natural ARE activator that functions by modifying Keap1 cysteine residues, but there are conflicting in vitro and in vivo data regarding which of these cysteine residues react. Although most biological data indicate that modification of C151 is essential for sulforaphane action, some recent studies using mass spectrometry have failed to identify C151 as a site of Keap1 sulforaphane reaction. We have reconciled these conflicting data using mass spectrometry with a revised sample preparation protocol and confirmed that C151 is indeed among the most readily modified cysteines of Keap1 by sulforaphane. Previous mass spectrometry-based studies used iodoacetamide during sample preparation to derivatize free cysteine sulfhydryl groups causing the loss of sulforaphane from highly reactive and reversible cysteine residues on Keap1 including C151. By omitting iodoacetamide from the protocol and reducing sample preparation time, our mass spectrometry-based studies now confirm previous cell-based studies which showed that sulforaphane reacts with at least four cysteine residues of Keap1 including C151.
Chemical Research in Toxicology 03/2011; 24(4):515-21. · 3.78 Impact Factor
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Yongsoo Choi,
Katherine Jermihov,
Sang-Jip Nam,
Megan Sturdy,
Katherine Maloney,
Xi Qiu,
Lucas R Chadwick,
Matthew Main,
Shao-Nong Chen, Andrew D Mesecar,
Norman R Farnsworth,
Guido F Pauli,
William Fenical,
John M Pezzuto,
Richard B van Breemen,
Richard R van Breemen
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ABSTRACT: Inhibitors of quinone reductase-2 (NQO2; QR-2) can have antimalarial activity and antitumor activities or can function as chemoprevention agents by preventing the metabolic activation of toxic quinones such as menadione. To expedite the search for new natural product inhibitors of QR-2, we developed a screening assay based on ultrafiltration liquid chromatography-mass spectrometry that is compatible with complex samples such as bacterial or botanical extracts. Human QR-2 was prepared recombinantly, and the known QR-2 inhibitor, resveratrol, was used as a positive control and as a competitive ligand to eliminate false positives. Ultrafiltration LC-MS screening of extracts of marine sediment bacteria resulted in the discovery of tetrangulol methyl ether as an inhibitor of QR-2. When applied to the screening of hop extracts from the botanical, Humulus lupulus L., xanthohumol and xanthohumol D were identified as ligands of QR-2. Inhibition of QR-2 by these ligands was confirmed using a functional enzyme assay. Furthermore, binding of xanthohumol and xanthohumol D to the active site of QR-2 was confirmed using X-ray crystallography. Ultrafiltration LC-MS was shown to be a useful assay for the discovery of inhibitors of QR-2 in complex matrixes such as extracts of bacteria and botanicals.
Analytical Chemistry 02/2011; 83(3):1048-52. · 5.86 Impact Factor
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Jian-Hong Yang,
Tamara P Kondratyuk,
Katherine C Jermihov,
Laura E Marler,
Xi Qiu,
Yongsoo Choi,
Hongmei Cao,
Rui Yu,
Megan Sturdy,
Rong Huang,
Ying Liu,
Li-Qin Wang, Andrew D Mesecar,
Richard B van Breemen,
John M Pezzuto,
Harry H S Fong,
Ye-Gao Chen,
Hong-Jie Zhang
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ABSTRACT: Phytochemical investigation of the whole plant of Lepisorus contortus (Christ) Ching led to the isolation of five new phenylethanoid glycosides (1-5), each containing a caffeoyl group, a new flavonoid glycoside (10), and 14 known compounds (6-9 and 11-15, syringic acid, vanillic acid, phloretic acid, diplopterol, and β-sitosterol). This is the first report of phenylethanoid glycosides from the family Polypodiaceae. Compounds 1-15 were evaluated for their cancer chemopreventive potential based on their ability to inhibit tumor necrosis factor alpha (TNF-α)-induced NF-κB activity, nitric oxide (NO) production, and aromatase, quinone reductase 2 (QR-2), and COX-1/-2 activities. Quercetin-3-O-β-d-glucoside (15) demonstrated inhibition against QR2 with an IC(50) value of 3.84 μM, which confirmed kaempferol/quercetin glycosides as the active compounds to inhibit QR2. The compound also demonstrated NF-κB activity with an IC(50) value of 33.6 μM. In addition, compounds 1, 2, 4, and 6 showed aromatase activity with IC(50) values of 30.7, 32.3, 26.8, and 35.3 μM, respectively.
Journal of Natural Products 01/2011; 74(2):129-36. · 3.13 Impact Factor
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ABSTRACT: The isolation of 2-bromo-1-hydroxyphenazine from a marine Streptomyces species, strain CNS284, and its activity against NF-κB, suggested that a short and flexible route for the synthesis of this metabolite and a variety of phenazine analogues should be developed. Numerous phenazines were subsequently prepared and evaluated as inducers of quinone reductase 1 (QR1) and inhibitors of quinone reductase 2 (QR2), NF-κB, and inducible nitric oxide synthase (iNOS). Several of the active phenazine derivatives displayed IC₅₀ values vs QR1 induction and QR2 inhibition in the nanomolar range, suggesting that they may find utility as cancer chemopreventive agents.
Journal of Medicinal Chemistry 12/2010; 53(24):8688-99. · 4.80 Impact Factor
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ABSTRACT: The Cullin3-based E3 ubiquitin ligase complex is thought to play an important role in the cellular response to oxidative stress and xenobiotic assault. While limited biochemical studies of the ligase's role in these complex signaling pathways are beginning to emerge, structural studies are lagging far behind due to the inability to acquire sufficient quantities of full-length, highly pure and active Cullin3. Here we describe the design and construction of an optimized expression and purification system for the full-length, human Cullin3-RINGBox 1 (Rbx1) protein complex from Escherichia coli. The dual-expression system is comprised of codon-optimized Cullin3 and Rbx1 genes co-expressed from a single pET-Duet-1 plasmid. Rapid purification of the Cullin3-Rbx1 complex is achieved in two steps via an affinity column followed by size-exclusion chromatography. Approximately 15mg of highly pure and active Cullin3-Rbx1 protein from 1L of E. coli culture can be achieved. Analysis of the quaternary structure of the Cullin3-Rbx1 and Cullin3-Rbx1-Keap1 complexes by size-exclusion chromatography and analytical ultracentrifugation indicates a 1:1 stoichiometry for the Cullin3-Rbx1 complex (MW=111kDa), and a 1:1:2 stoichiometry for the Cullin3-Rbx1-Keap1 complex (MW=280kDa). This latter complex has a novel quaternary structural organization for cullin E3 ligases, and it is fully active based on an in vitro Cullin3-Rbx1-Keap1-Nrf2 ubiquitination activity assay that was developed and optimized in this study.
Biochemical and Biophysical Research Communications 10/2010; 400(4):471-5. · 2.48 Impact Factor
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ABSTRACT: A series of new resveratrol analogues were designed and synthesized and their inhibitory activities against aromatase were evaluated. The crystal structure of human aromatase (PDB 3eqm) was used to rationalize the mechanism of action of the aromatase inhibitor 32 (IC50 0.59 microM) through docking, molecular mechanics energy minimization, and computer graphics molecular modeling, and the information was utilized to design several very potent inhibitors, including compounds 82 (IC50 70 nM) and 84 (IC50 36 nM). The aromatase inhibitory activities of these compounds are much more potent than that for the lead compound resveratrol, which has an IC50 of 80 microM. In addition to aromatase inhibitory activity, compounds 32 and 44 also displayed potent QR2 inhibitory activity (IC50 1.7 microM and 0.27 microM, respectively) and the high-resolution X-ray structures of QR2 in complex with these two compounds provide insight into their mechanism of QR2 inhibition. The aromatase and quinone reductase inhibitors resulting from these studies have potential value in the treatment and prevention of cancer.
Bioorganic & medicinal chemistry 07/2010; 18(14):5352-66. · 2.82 Impact Factor
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Arun K Ghosh,
Jun Takayama,
Kalapala Venkateswara Rao,
Kiira Ratia,
Rima Chaudhuri,
Debbie C Mulhearn,
Hyun Lee,
Daniel B Nichols,
Surendranath Baliji,
Susan C Baker,
Michael E Johnson, Andrew D Mesecar
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ABSTRACT: The design, synthesis, X-ray crystal structure, molecular modeling, and biological evaluation of a series of new generation SARS-CoV PLpro inhibitors are described. A new lead compound 3 (6577871) was identified via high-throughput screening of a diverse chemical library. Subsequently, we carried out lead optimization and structure-activity studies to provide a series of improved inhibitors that show potent PLpro inhibition and antiviral activity against SARS-CoV infected Vero E6 cells. Interestingly, the (S)-Me inhibitor 15 h (enzyme IC(50) = 0.56 microM; antiviral EC(50) = 9.1 microM) and the corresponding (R)-Me 15 g (IC(50) = 0.32 microM; antiviral EC(50) = 9.1 microM) are the most potent compounds in this series, with nearly equivalent enzymatic inhibition and antiviral activity. A protein-ligand X-ray structure of 15 g-bound SARS-CoV PLpro and a corresponding model of 15 h docked to PLpro provide intriguing molecular insight into the ligand-binding site interactions.
Journal of Medicinal Chemistry 07/2010; 53(13):4968-79. · 4.80 Impact Factor
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ABSTRACT: 4-Oxalocrotonate tautomerase (4-OT) isozymes play prominent roles in the bacterial utilization of aromatic hydrocarbons as sole carbon sources. These enzymes catalyze the conversion of 2-hydroxy-2,4-hexadienedioate (or 2-hydroxymuconate) to 2-oxo-3-hexenedioate, where Pro-1 functions as a general base and shuttles a proton from the 2-hydroxyl group of the substrate to the C-5 position of the product. 4-OT, a homohexamer from Pseudomonas putida mt-2, is the most extensively studied 4-OT isozyme and the founding member of the tautomerase superfamily. A search of five thermophilic bacterial genomes identified a coded amino acid sequence in each that had been annotated as a tautomerase-like protein but lacked Pro-1. However, a nearby sequence has Pro-1, but the sequence is not annotated as a tautomerase-like protein. To characterize this group of proteins, two genes from Chloroflexus aurantiacus J-10-fl were cloned, and the corresponding proteins were expressed. Kinetic, biochemical, and X-ray structural analyses show that the two expressed proteins form a functional heterohexamer 4-OT (hh4-OT), composed of three alphabeta dimers. Like the P. putida enzyme, hh4-OT requires the amino-terminal proline and two arginines for the conversion of 2-hydroxymuconate to the product, implicating an analogous mechanism. In contrast to 4-OT, hh4-OT does not exhibit the low-level activity of another tautomerase superfamily member, the heterohexamer trans-3-chloroacrylic acid dehalogenase (CaaD). Characterization of hh4-OT enables functional assignment of the related enzymes, highlights the diverse ways the beta-alpha-beta building block can be assembled into an active enzyme, and provides further insight into the molecular basis of the low-level CaaD activity in 4-OT.
Biochemistry 06/2010; 49(24):5016-27. · 3.42 Impact Factor
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ABSTRACT: Resveratrol has demonstrated cancer chemopreventive activity in animal models and some clinical trials are underway. In addition, resveratrol was shown to promote cell survival, increase lifespan and mimic caloric restriction, thereby improving health and survival of mice on high-calorie diet. All of these effects are potentially mediated by the pleiotropic interactions of resveratrol with different enzyme targets including COX-1 (cyclo-oxygenase-1) and COX-2, NAD+-dependent histone deacetylase SIRT1 (sirtuin 1) and QR2 (quinone reductase 2). Nonetheless, the health benefits elicited by resveratrol as a direct result of these interactions with molecular targets have been questioned, since it is rapidly and extensively metabolized to sulfate and glucuronide conjugates, resulting in low plasma concentrations. To help resolve these issues, we tested the ability of resveratrol and its metabolites to modulate the function of some known targets in vitro. In the present study, we have shown that COX-1, COX-2 and QR2 are potently inhibited by resveratrol, and that COX-1 and COX-2 are also inhibited by the resveratrol 4'-O-sulfate metabolite. We determined the X-ray structure of resveratrol bound to COX-1 and demonstrate that it occupies the COX active site similar to other NSAIDs (non-steroidal anti-inflammatory drugs). Finally, we have observed that resveratrol 3- and 4'-O-sulfate metabolites activate SIRT1 equipotently to resveratrol, but that activation is probably a substrate-dependent phenomenon with little in vivo relevance. Overall, the results of this study suggest that in vivo an interplay between resveratrol and its metabolites with different molecular targets may be responsible for the overall beneficial health effects previously attributed only to resveratrol itself.
Biochemical Journal 05/2010; 429(2):273-82. · 4.90 Impact Factor
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Jian-Hong Yang,
Tamara P Kondratyuk,
Laura E Marler,
Xi Qiu,
Yongsoo Choi,
Hongmei Cao,
Rui Yu,
Megan Sturdy,
Scott Pegan,
Ying Liu,
Li-Qin Wang, Andrew D Mesecar,
Richard B Van Breemen,
John M Pezzuto,
Harry H S Fong,
Ye-Gao Chen,
Hong-Jie Zhang
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ABSTRACT: Kaempferol glycosides, named palmatosides A (1), B (2) and C (3), together with three known kaempferol glycosides, multiflorins A (4) and B (5), and afzelin (6), were isolated from the roots of the fern Neocheiropteris palmatopedata. Palmatosides A (1) and B (2) each possessed an unusual sugar moiety containing a 4,4-dimethyl-3-oxo-butoxy substituent group. The isolated compounds were evaluated for their cancer chemopreventive potential based on their ability to inhibit tumor necrosis factor alpha (TNF-alpha)-induced NF-kappaB activity, nitric oxide (NO) production, aromatase, quinone reductase 2 (QR2) and COX-1/-2 activities. Palmatosides B (2) and C (3) inhibited TNF-alpha-induced NF-kappaB activity with IC(50) values of 15.7 and 24.1 microM, respectively; multiflorin A (4) inhibited aromatase enzyme with an IC(50) value of 15.5 microM; afzelin (6) showed 68.3% inhibition against QR2 at a concentration of 11.5 microg/ml; palmatoside A (1) showed 52% inhibition against COX-1 enzyme at a concentration of 10 microg/ml; and multiflorin B (5) showed 52% inhibition against nitric oxide production at a concentration of 20 microg/ml. In addition, compounds 3-6 were shown to bind QR2 enzyme using LC-MS ultrafiltration binding assay.
Phytochemistry 04/2010; 71(5-6):641-7. · 3.35 Impact Factor
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Mark A Clementz,
Zhongbin Chen,
Bridget S Banach,
Yanhua Wang,
Li Sun,
Kiira Ratia,
Yahira M Baez-Santos,
Jie Wang,
Jun Takayama,
Arun K Ghosh,
Kui Li, Andrew D Mesecar,
Susan C Baker
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ABSTRACT: Coronaviruses encode multifunctional proteins that are critical for viral replication and for blocking the innate immune response to viral infection. One such multifunctional domain is the coronavirus papain-like protease (PLP), which processes the viral replicase polyprotein, has deubiquitinating (DUB) activity, and antagonizes the induction of type I interferon (IFN). Here we characterized the DUB and IFN antagonism activities of the PLP domains of human coronavirus NL63 and severe acute respiratory syndrome (SARS) coronavirus to determine if DUB activity mediates interferon antagonism. We found that NL63 PLP2 deconjugated ubiquitin (Ub) and the Ub-line molecule ISG15 from cellular substrates and processed both lysine-48- and lysine-63- linked polyubiquitin chains. This PLP2 DUB activity was dependent on an intact catalytic cysteine residue. We demonstrated that in contrast to PLP2 DUB activity, PLP2-mediated interferon antagonism did not require enzymatic activity. Furthermore, addition of an inhibitor that blocks coronavirus protease/DUB activity did not abrogate interferon antagonism. These results indicated that a component of coronavirus PLP-mediated interferon antagonism was independent of protease and DUB activity. Overall, these results demonstrate the multifunctional nature of the coronavirus PLP domain as a viral protease, DUB, and IFN antagonist and suggest that these independent activities may provide multiple targets for antiviral therapies.
Journal of Virology 02/2010; 84(9):4619-29. · 5.40 Impact Factor
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ABSTRACT: The malachite green assay is often used for measuring the presence of inorganic mono-phosphate concentrations. Some studies have adapted this assay for use in monitoring enzymatic reactions and have suggested its potential use in high throughput screening (HTS). With the increasing availability of laboratory automation, some studies are starting to explore the possibility of conducting limited, semi-automated versions of the assay. Here we report the optimization and complete adaptation of the malachite green assay to a fully automated, HTS platform that can be performed unattended with standard, commercially available, automated liquid-handling systems. The assay is universal for the majority of enzymes that release phosphate or pyrophosphate. Moreover, the assay is fully scalable from smaller drug screening efforts ( approximately 20,000 wells per day) to ultra-high throughput environments ( approximately 200,000 wells per day). The assay uses cost-effective, commercially available reagents, and can be used to perform automated IC50 value and kinetic parameter determination. Finally, we demonstrate the utility of the assay via the initial, primary screening of 100,080 compounds against two target enzymes from Bacillus anthracis, O-succinylbenzoyl-CoA synthetase and nicotinate mononucleotide adenylyltransferase.
Combinatorial chemistry & high throughput screening 01/2010; 13(1):27-38. · 2.46 Impact Factor
