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Verma M, Trivedi L, Vasudev PG. Interaction Patterns of Pyrazolopyrimidines with Receptor Proteins. J Chem Inf Model 2023; 63:2331-2344. [PMID: 37023262 DOI: 10.1021/acs.jcim.2c01315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
Abstract
Heterocyclic compounds have a prominent role in medicinal chemistry and drug design. They are not only useful as medicinally active compounds but also as a modular structural scaffold for drug design. Therefore, heterocycles are present in many ligands that exhibit a broad spectrum of biological activities. Pyazolopyrimidines are nitrogen heterocycles and are part of many biologically active compounds and marketed drugs. This study examines the non-covalent interactions between the pyrazolopyrimidine rings and receptor proteins through data mining and analysis of high-resolution crystal structures deposited in the Protein Data Bank. The Protein Data Bank contains 471 crystal structures with pyrazolopyrimidine derivatives as ligands, among which 50% contains 1H-pyrazolo[3,4-d]pyrimidines (Pyp1), while 38% contains pyrazolo[1,5-a] pyrimidines (Pyp2). 1H-Pyrazolo[4,3-d]pyrimidines (Pyp3) are found in 11% of the structures, and no structural data is available for pyrazolo[1,5-c]pyrimidine isomers (Pyp4). Among receptor proteins, transferases are found in most examples (67.5%), followed by hydrolases (13.4%) and oxidoreductases (8.9%). Detailed analysis of structures to identify the most prevalent interactions of pyrazolopyrimidines with proteins shows that aromatic π···π interactions are present in ∼91% of the structures and hydrogen bonds/other polar contacts are present in ∼73% of the structures. The centroid-centroid distances (dcent) between the pyrazolopyrimidine rings and aromatic side chains of the proteins have been retrieved from crystal structures recorded at a high resolution (data resolution <2.0 Å). The average value of dcent in pyrazolopyrimidine-protein complexes is 5.32 Å. The information on the geometric parameters of aromatic interactions between the core pyrazolopyrimidine ring and the protein would be helpful in future in silico modeling studies on pyrazolopyrimidine-receptor complexes.
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Affiliation(s)
- Meenakshi Verma
- Plant Biotechnology Division, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow 226015, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 220025, India
| | - Laxmikant Trivedi
- Plant Biotechnology Division, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow 226015, India
| | - Prema G Vasudev
- Plant Biotechnology Division, CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow 226015, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 220025, India
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Luna G, Dolzhenko AV, Mancera RL. Inhibitors of Xanthine Oxidase: Scaffold Diversity and Structure-Based Drug Design. ChemMedChem 2019; 14:714-743. [PMID: 30740924 DOI: 10.1002/cmdc.201900034] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Indexed: 12/19/2022]
Abstract
Xanthine oxidase (XO) is the enzyme responsible for the catabolism of purines and their conversion into uric acid. XO is thus the target for the treatment of hyperuricemia and gout. For more than 50 years the only XO inhibitor drug available on the market was the purine analogue allopurinol. In the last decade there has been a resurgence in the search for new inhibitors of XO, as the activity of XO and hyperuricemia have also been associated with a variety of conditions such as diabetes, hypertension, and other cardiovascular diseases. In recent years the non-purine inhibitor febuxostat was approved in Europe and the USA for the treatment of hyperuricemia. This drug was followed by another XO inhibitor called topiroxostat. This review discusses the molecular structures and activities of the multiple classes of inhibitors that have been developed since the discovery of allopurinol, with a brief review of the molecular interactions between inhibitors and XO active site residues for the most important molecules. The challenges ahead for the discovery of new inhibitors of XO with novel chemical structures are discussed.
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Affiliation(s)
- Giuseppe Luna
- School of Pharmacy and Biomedical Sciences and Curtin Health Innovation Research Institute, Curtin University, GPO Box U1987, Perth, WA, 6845, Australia
| | - Anton V Dolzhenko
- School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, Selangor Darul Ehsan, 47500, Malaysia
| | - Ricardo L Mancera
- School of Pharmacy and Biomedical Sciences and Curtin Health Innovation Research Institute, Curtin University, GPO Box U1987, Perth, WA, 6845, Australia
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Effects of Toona sinensis Leaf Extract and Its Chemical Constituents on Xanthine Oxidase Activity and Serum Uric Acid Levels in Potassium Oxonate-Induced Hyperuricemic Rats. Molecules 2018; 23:molecules23123254. [PMID: 30544886 PMCID: PMC6321014 DOI: 10.3390/molecules23123254] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 12/06/2018] [Accepted: 12/08/2018] [Indexed: 01/10/2023] Open
Abstract
Toona sinensis leaf is used as a seasonal vegetable in Korea. A 70% ethanol extract of these leaves exhibited potent xanthine oxidase (XO) inhibition, with a 50% inhibitory concentration (IC50) of 78.4 µM. To investigate the compounds responsible for this effect, bioassay-guided purification led to the isolation of five constituents, identified as quercetin-3-O-rutinoside, quercetin-3-O-β-d-glucopyranoside, 1,2,3,4,6-penta-O-galloyl-β-d-glucopyranose (compound 3), quercetin-3-O-α-l-rhamnopyranoside, and kaempferol-3-O-α-l-rhamnopyranoside. Compound 3 showed the most potent inhibition of XO, with an IC50 of 2.8 µM. This was similar to that of allopurinol (IC50 = 2.3 µM), which is used clinically to treat hyperuricemia. Kinetic analyses found that compound 3 was a reversible noncompetitive XO inhibitor. In vivo, the T. sinensis leaf extract (300 mg/kg), or compound 3 (40 mg/kg), significantly decreased serum uric acid levels in rats with potassium oxonate-induced hyperuricemia. Furthermore, ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry analysis identified a high level of compound 3 in the leaf extract. These findings suggest that T. sinensis leaves could be developed to produce nutraceutical preparations.
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Nile SH, Keum YS, Nile AS, Kwon YD, Kim DH. Potential cow milk xanthine oxidase inhibitory and antioxidant activity of selected phenolic acid derivatives. J Biochem Mol Toxicol 2017; 32. [DOI: 10.1002/jbt.22005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 09/21/2017] [Accepted: 09/26/2017] [Indexed: 12/31/2022]
Affiliation(s)
- Shivraj Hariram Nile
- Department of Bioresources and Food Science, College of Life and Environmental Sciences; Konkuk University; Seoul 05029 Republic of Korea
- Department of Crop Science, Sanghuh College of Life Sciences; Konkuk University; Seoul 05029 Republic of Korea
| | - Young Soo Keum
- Department of Crop Science, Sanghuh College of Life Sciences; Konkuk University; Seoul 05029 Republic of Korea
| | - Arti Shivraj Nile
- Department of Bioresources and Food Science, College of Life and Environmental Sciences; Konkuk University; Seoul 05029 Republic of Korea
| | - Young Deuk Kwon
- Department of Bioresources and Food Science, College of Life and Environmental Sciences; Konkuk University; Seoul 05029 Republic of Korea
| | - Doo Hwan Kim
- Department of Bioresources and Food Science, College of Life and Environmental Sciences; Konkuk University; Seoul 05029 Republic of Korea
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Belaroussi R, El Hakmaoui A, Akssira M, Guillaumet G, Routier S. Regioselective Synthesis of 2,4-Substituted Pyrido[1′,2′:1,5]pyrazolo[3,4-d
]pyrimidines through Sequential Pd-Catalyzed Arylation and SN
Ar Reactions. European J Org Chem 2016. [DOI: 10.1002/ejoc.201600356] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Rabia Belaroussi
- Univ Orleans; CNRS; Institut de Chimie Organique et Analytique; UMR 7311; BP 6759 45067 Orléans Cedex 2 France
- Laboratoire de Chimie Physique et Chimie Bioorganique; Université Hassan II-Mohammedia-Casablanca; B. P. 146 28800 Mohammedia Morocco
| | - Ahmed El Hakmaoui
- Laboratoire de Chimie Physique et Chimie Bioorganique; Université Hassan II-Mohammedia-Casablanca; B. P. 146 28800 Mohammedia Morocco
| | - Mohamed Akssira
- Laboratoire de Chimie Physique et Chimie Bioorganique; Université Hassan II-Mohammedia-Casablanca; B. P. 146 28800 Mohammedia Morocco
| | - Gérald Guillaumet
- Univ Orleans; CNRS; Institut de Chimie Organique et Analytique; UMR 7311; BP 6759 45067 Orléans Cedex 2 France
| | - Sylvain Routier
- Univ Orleans; CNRS; Institut de Chimie Organique et Analytique; UMR 7311; BP 6759 45067 Orléans Cedex 2 France
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Foti RS, Dalvie DK. Cytochrome P450 and Non-Cytochrome P450 Oxidative Metabolism: Contributions to the Pharmacokinetics, Safety, and Efficacy of Xenobiotics. ACTA ACUST UNITED AC 2016; 44:1229-45. [PMID: 27298339 DOI: 10.1124/dmd.116.071753] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/10/2016] [Indexed: 12/16/2022]
Abstract
The drug-metabolizing enzymes that contribute to the metabolism or bioactivation of a drug play a crucial role in defining the absorption, distribution, metabolism, and excretion properties of that drug. Although the overall effect of the cytochrome P450 (P450) family of drug-metabolizing enzymes in this capacity cannot be understated, advancements in the field of non-P450-mediated metabolism have garnered increasing attention in recent years. This is perhaps a direct result of our ability to systematically avoid P450 liabilities by introducing chemical moieties that are not susceptible to P450 metabolism but, as a result, may introduce key pharmacophores for other drug-metabolizing enzymes. Furthermore, the effects of both P450 and non-P450 metabolism at a drug's site of therapeutic action have also been subject to increased scrutiny. To this end, this Special Section on Emerging Novel Enzyme Pathways in Drug Metabolism will highlight a number of advancements that have recently been reported. The included articles support the important role of non-P450 enzymes in the clearance pathways of U.S. Food and Drug Administration-approved drugs over the past 10 years. Specific examples will detail recent reports of aldehyde oxidase, flavin-containing monooxygenase, and other non-P450 pathways that contribute to the metabolic, pharmacokinetic, or pharmacodynamic properties of xenobiotic compounds. Collectively, this series of articles provides additional support for the role of non-P450-mediated metabolic pathways that contribute to the absorption, distribution, metabolism, and excretion properties of current xenobiotics.
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Affiliation(s)
- Robert S Foti
- Pharmacokinetics and Drug Metabolism, Amgen, Cambridge, Massachusetts (R.S.F.); and Pharmacokinetics, Dynamics, and Metabolism, Pfizer, La Jolla, California (D.K.D.)
| | - Deepak K Dalvie
- Pharmacokinetics and Drug Metabolism, Amgen, Cambridge, Massachusetts (R.S.F.); and Pharmacokinetics, Dynamics, and Metabolism, Pfizer, La Jolla, California (D.K.D.)
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Liang X, Tang Y, Duan L, Cheng S, Luo L, Cao X, Tu B. Adverse effect of sub-chronic exposure to benzo(a)pyrene and protective effect of butylated hydroxyanisole on learning and memory ability in male Sprague-Dawley rat. J Toxicol Sci 2014; 39:739-48. [DOI: 10.2131/jts.39.739] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Xiao Liang
- Department of Occupational and Environmental Medicine, School of Public Health, Chongqing Medical University
| | - Yan Tang
- Department of Occupational and Environmental Medicine, School of Public Health, Luzhou Medical College
| | - Li Duan
- Department of Occupational and Environmental Medicine, School of Public Health, Chongqing Medical University
| | - Shuqun Cheng
- Department of Occupational and Environmental Medicine, School of Public Health, Chongqing Medical University
| | - Long Luo
- Department of Occupational and Environmental Medicine, School of Public Health, Chongqing Medical University
| | - Xianqing Cao
- Experiment center, School of Public Health, Chongqing Medical University
| | - Baijie Tu
- Department of Occupational and Environmental Medicine, School of Public Health, Chongqing Medical University
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Zhang Z, Li J, Yang L, Chen R, Yang R, Zhang H, Cai D, Chen H. The cytotoxic role of intermittent high glucose on apoptosis and cell viability in pancreatic beta cells. J Diabetes Res 2014; 2014:712781. [PMID: 24772447 PMCID: PMC3977095 DOI: 10.1155/2014/712781] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 02/02/2014] [Accepted: 02/09/2014] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVES Glucose fluctuations are both strong predictor of diabetic complications and crucial factor for beta cell damages. Here we investigated the effect of intermittent high glucose (IHG) on both cell apoptosis and proliferation activity in INS-1 cells and the potential mechanisms. METHODS Cells were treated with normal glucose (5.5 mmol/L), constant high glucose (CHG) (25 mmol/L), and IHG (rotation per 24 h in 11.1 or 25 mmol/L) for 7 days. Reactive oxygen species (ROS), xanthine oxidase (XOD) level, apoptosis, cell viability, cell cycle, and expression of cyclinD1, p21, p27, and Skp2 were determined. RESULTS We found that IHG induced more significant apoptosis than CHG and normal glucose; intracellular ROS and XOD levels were more markedly increased in cells exposed to IHG. Cells treated with IHG showed significant decreased cell viability and increased cell proportion in G0/G1 phase. Cell cycle related proteins such as cyclinD1 and Skp2 were decreased significantly, but expressions of p27 and p21 were increased markedly. CONCLUSIONS This study suggested that IHG plays a more toxic effect including both apoptosis-inducing and antiproliferative effects on INS-1 cells. Excessive activation of cellular stress and regulation of cyclins might be potential mechanism of impairment in INS-1 cells induced by IHG.
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Affiliation(s)
- Zhen Zhang
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China
| | - Jing Li
- Department of Endocrinology, Nanshan Affiliated Hospital of Guangdong Medical College, Shenzhen 518052, China
| | - Lei Yang
- Department of Nephrology, Zhujiang Hospital of Southern Medical University, Guangzhou 510282, China
| | - Rongping Chen
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China
| | - Rui Yang
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China
| | - Hua Zhang
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China
| | - Dehong Cai
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China
| | - Hong Chen
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China
- *Hong Chen:
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Xanthine oxidase does not contribute to apoptosis after brain hypoxia-ischemia in immature rabbits. ISRN NEUROSCIENCE 2013; 2013:253093. [PMID: 24967305 PMCID: PMC4045541 DOI: 10.1155/2013/253093] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 07/11/2013] [Indexed: 12/12/2022]
Abstract
Background. The mechanisms involving the initiation of apoptosis after brain hypoxia-ischemia through caspase activation are not fully defined. Oxygen free radicals may be an important mediator of caspase initiation with reactive oxygen species generated by xanthine oxidase (XO) being one potential source. The purpose of this study was to examine the role of XO in apoptosis after global cerebral injury. Methods. Immature rabbits were subjected to 8 minutes hypoxia and 8 minutes ischemia and then 4 hours of reperfusion. In one group (n = 5), the XO substrate xanthine was infused to generate more oxygen free radicals to promote apoptosis while in another (n = 5), the XO inhibitor allopurinol was given to reduce apoptosis by preventing free radical production (n = 5). Control animals (n = 4) received the vehicles. Caspase 3, 8, and 9 enzyme activities were measured in the cerebral cortex, hippocampus, cerebellum, thalamus, and caudate. Results. Administration of xanthine increased (P < 0.05) caspase 3 activity but only in the hippocampus, and pretreatment with allopurinol did not reduce it. No differences (P > 0.05) were found in any other region nor were there any changes in caspases 8 or 9 activities. Conclusion. We conclude that XO is not a major factor in inducing apoptosis after hypoxic-ischemic brain injury.
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Obach RS. Pharmacologically active drug metabolites: impact on drug discovery and pharmacotherapy. Pharmacol Rev 2013; 65:578-640. [PMID: 23406671 DOI: 10.1124/pr.111.005439] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Metabolism represents the most prevalent mechanism for drug clearance. Many drugs are converted to metabolites that can retain the intrinsic affinity of the parent drug for the pharmacological target. Drug metabolism redox reactions such as heteroatom dealkylations, hydroxylations, heteroatom oxygenations, reductions, and dehydrogenations can yield active metabolites, and in rare cases even conjugation reactions can yield an active metabolite. To understand the contribution of an active metabolite to efficacy relative to the contribution of the parent drug, the target affinity, functional activity, plasma protein binding, membrane permeability, and pharmacokinetics of the active metabolite and parent drug must be known. Underlying pharmacokinetic principles and clearance concepts are used to describe the dispositional behavior of metabolites in vivo. A method to rapidly identify active metabolites in drug research is described. Finally, over 100 examples of drugs with active metabolites are discussed with regard to the importance of the metabolite(s) in efficacy and safety.
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Affiliation(s)
- R Scott Obach
- Pfizer Inc., Eastern Point Rd., Groton, CT 06340, USA.
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Bytyqi-Damoni A, Genç H, Zengin M, Beyaztas S, Gençer N, Arslan O. In vitroeffect of novel β-lactam compounds on xanthine oxidase enzyme activity. ACTA ACUST UNITED AC 2012; 40:369-77. [DOI: 10.3109/10731199.2012.678943] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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A new method for the quantification of superoxide dismutase mimics with an allopurinol–xanthine oxidase–lucigenin enhanced system. J Biol Inorg Chem 2011; 16:753-61. [DOI: 10.1007/s00775-011-0777-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Accepted: 03/24/2011] [Indexed: 10/18/2022]
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Kelley EE, Batthyany CI, Hundley NJ, Woodcock SR, Bonacci G, Del Rio JM, Schopfer FJ, Lancaster JR, Freeman BA, Tarpey MM. Nitro-oleic acid, a novel and irreversible inhibitor of xanthine oxidoreductase. J Biol Chem 2008; 283:36176-84. [PMID: 18974051 DOI: 10.1074/jbc.m802402200] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Xanthine oxidoreductase (XOR) generates proinflammatory oxidants and secondary nitrating species, with inhibition of XOR proving beneficial in a variety of disorders. Electrophilic nitrated fatty acid derivatives, such as nitro-oleic acid (OA-NO2), display anti-inflammatory effects with pleiotropic properties. Nitro-oleic acid inhibits XOR activity in a concentration-dependent manner with an IC50 of 0.6 microM, limiting both purine oxidation and formation of superoxide (O2.). Enzyme inhibition by OA-NO2 is not reversed by thiol reagents, including glutathione, beta-mercaptoethanol, and dithiothreitol. Structure-function studies indicate that the carboxylic acid moiety, nitration at the 9 or 10 olefinic carbon, and unsaturation is required for XOR inhibition. Enzyme turnover and competitive reactivation studies reveal inhibition of electron transfer reactions at the molybdenum cofactor accounts for OA-NO2-induced inhibition. Importantly, OA-NO2 more potently inhibits cell-associated XOR-dependent O2. production than does allopurinol. Combined, these data establish a novel role for OA-NO2 in the inhibition of XOR-derived oxidant formation.
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Affiliation(s)
- Eric E Kelley
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
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Chaves S, Gil M, Canário S, Jelic R, Romão MJ, Trincão J, Herdtweck E, Sousa J, Diniz C, Fresco P, Santos MA. Biologically relevant O,S-donor compounds. Synthesis, molybdenum complexation and xanthine oxidase inhibition. Dalton Trans 2008:1773-82. [DOI: 10.1039/b717172b] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Tamta H, Kalra S, Thilagavathi R, Chakraborti AK, Mukhopadhyay AK. Nature and position of functional group on thiopurine substrates influence activity of xanthine oxidase--enzymatic reaction pathways of 6-mercaptopurine and 2-mercaptopurine are different. BIOCHEMISTRY (MOSCOW) 2007; 72:170-7. [PMID: 17367294 DOI: 10.1134/s000629790702006x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Xanthine oxidase-catalyzed hydroxylation reactions of the anticancer drug 6-mercaptopurine (6-MP) and its analog 2-mercaptopurine (2-MP) as well as 6-thioxanthine (6-TX) and 2-thioxanthine (2-TX) have been studied using UV-spectroscopy, high pressure liquid chromatography, photodiode array, and liquid chromatography-based mass spectral analysis. It is shown that 6-MP and 2-MP are oxidatively hydroxylated through different pathways. Enzymatic hydroxylation of 6-MP forms 6-thiouric acid in two steps involving 6-TX as the intermediate, whereas 2-MP is converted to 8-hydroxy-2-mercaptopurine as the expected end product in one step. Surprisingly, in contrast to the other thiopurines, enzymatic hydroxylation of 2-MP showed a unique hyperchromic effect at 264 nm as the reaction proceeded. However, when 2-TX is used as the substrate, it is hydroxylated to 2-thiouric acid. The enzymatic hydroxylation of 2-MP is considerably faster than that of 6-MP, while 6-TX and 2-TX show similar rates under identical reaction conditions. The reason why 2-MP is a better substrate than 6-MP and how the chemical nature and position of the functional groups present on the thiopurine substrates influence xanthine oxidase activity are discussed.
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Affiliation(s)
- Hemlata Tamta
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Sector 67, SAS Nagar, Punjab, India.
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Kalra S, Jena G, Tikoo K, Mukhopadhyay AK. Preferential inhibition of xanthine oxidase by 2-amino-6-hydroxy-8-mercaptopurine and 2-amino-6-purine thiol. BMC BIOCHEMISTRY 2007; 8:8. [PMID: 17511860 PMCID: PMC1885804 DOI: 10.1186/1471-2091-8-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Accepted: 05/18/2007] [Indexed: 01/27/2023]
Abstract
Background The anticancer drug, 6-mercaptopurine (6MP) is subjected to metabolic clearance through xanthine oxidase (XOD) mediated hydroxylation, producing 6-thiouric acid (6TUA), which is excreted in urine. This reduces the effective amount of drug available for therapeutic efficacy. Co-administration of allopurinol, a suicide inhibitor of XOD, which blocks the hydroxylation of 6MP inadvertently enhances the 6MP blood level, counters this reduction. However, allopurinol also blocks the hydroxylation of hypoxanthine, xanthine (released from dead cancer cells) leading to their accumulation in the body causing biochemical complications such as xanthine nephropathy. This necessitates the use of a preferential XOD inhibitor that selectively inhibits 6MP transformation, but leaves xanthine metabolism unaffected. Results Here, we have characterized two such unique inhibitors namely, 2-amino-6-hydroxy-8-mercaptopurine (AHMP) and 2-amino-6-purinethiol (APT) on the basis of IC50 values, residual activity in bi-substrate simulative reaction and the kinetic parameters like Km, Ki, kcat. The IC50 values of AHMP for xanthine and 6MP as substrate are 17.71 ± 0.29 μM and 0.54 ± 0.01 μM, respectively and the IC50 values of APT for xanthine and 6MP as substrates are 16.38 ± 0.21 μM and 2.57 ± 0.08 μM, respectively. The Ki values of XOD using AHMP as inhibitor with xanthine and 6MP as substrate are 5.78 ± 0.48 μM and 0.96 ± 0.01 μM, respectively. The Ki values of XOD using APT as inhibitor with xanthine and 6MP as substrate are 6.61 ± 0.28 μM and 1.30 ± 0.09 μM. The corresponding Km values of XOD using xanthine and 6MP as substrate are 2.65 ± 0.02 μM and 6.01 ± 0.03 μM, respectively. The results suggest that the efficiency of substrate binding to XOD and its subsequent catalytic hydroxylation is much superior for xanthine in comparison to 6MP. In addition, the efficiency of the inhibitor binding to XOD is much more superior when 6MP is the substrate instead of xanthine. We further undertook the toxicological evaluation of these inhibitors in a single dose acute toxicity study in mice and our preliminary experimental results suggested that the inhibitors were equally non-toxic in the tested doses. Conclusion We conclude that administration of either APT or AHMP along with the major anti-leukemic drug 6MP might serve as a good combination cancer chemotherapy regimen.
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Affiliation(s)
- Sukirti Kalra
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, Phase X, S.A.S Nagar, Mohali, Punjab,160062 India
| | - Gopabandhu Jena
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, Phase X, S.A.S Nagar, Mohali, Punjab, 160062 India
| | - Kulbhushan Tikoo
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, Phase X, S.A.S Nagar, Mohali, Punjab, 160062 India
| | - Anup Kumar Mukhopadhyay
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, Phase X, S.A.S Nagar, Mohali, Punjab, 160062 India
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Hsieh JF, Wu SH, Yang YL, Choong KF, Chen ST. The screening and characterization of 6-aminopurine-based xanthine oxidase inhibitors. Bioorg Med Chem 2007; 15:3450-6. [PMID: 17379526 DOI: 10.1016/j.bmc.2007.03.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Revised: 03/05/2007] [Accepted: 03/05/2007] [Indexed: 11/20/2022]
Abstract
Xanthine oxidase (XO) is a key enzyme which can catalyze xanthine to uric acid causing hyperuricemia in humans. By using the fractionation technique and inhibitory activity assay, an active compound that prevents XO from reacting with xanthine was isolated from wheat leaf. It was identified by the Mass and NMR as 6-aminopurine (adenine). A structure-activity study based on 6-aminopurine was conducted. The inhibition of XO activity by 6-aminopurine (IC(50)=10.89+/-0.13 microM) and its analogues was compared with that by allopurinol (IC(50)=7.82+/-0.12 microM). Among these analogues, 2-chloro-6(methylamino)purine (IC(50)=10.19+/-0.10 microM) and 4-aminopyrazolo[3,4-d] pyrimidine (IC(50)=30.26+/-0.23 microM) were found to be potent inhibitors of XO. Kinetics study showed that 2-chloro-6(methylamino)purine is non-competitive, while 4-aminopyrazolo[3,4-d]pyrimidine is competitive against XO.
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Affiliation(s)
- Jung-Feng Hsieh
- Institute of Biological Chemistry and the Genomics Research Center, Academia Sinica, Nankang, Taipei 115, Taiwan
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