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Inhibition Data (inhibition + data)
Selected AbstractsPoly- l -proline type II peptide mimics as probes of the active site occupancy requirements of cGMP-dependent protein kinaseCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2005R. Zhang Abstract:, Based on the X-ray crystal structure of cAMP-dependent protein kinase (PKA) with the endogenous inhibitor PKI and the X-ray crystal structure of cyclin-dependent kinase 2 (CDK2) with a substrate peptide, a proposal is put forth that some protein kinases bind peptide substrates in their active sites in the poly- l -proline type II (PPII) conformation. In this work, PPII peptide mimics are evaluated as pseudosubstrate inhibitors of cGMP-dependent protein kinase (PKG) to explore if PKG also binds peptide substrates in the PPII conformation. Inhibition data of our PPII mimetics provide evidence that the P , 1, P , 2, and P , 3 residues of substrate peptides bind in the PPII conformation (, approximately ,75°, , approximately 145°). In addition, the inhibition data also suggest that the P , 1, P , 2, and P , 3 residues in substrate peptides bind with a gauche(,) ,1 angle. [source] Sequence dependence of cell growth inhibition by EGFR,tyrosine kinase inhibitor ZD1839, docetaxel, and cisplatin in head and neck cancerHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 10 2009Carmen M. Klass MD Abstract Background This study was to explore whether the efficacy of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor ZD1839 (Z, Iressa, gefitinib) plus chemotherapeutic agents docetaxel (D) and cisplatin (P) may benefit from sequencing of the combination. Methods Three head and neck cancer cell lines were used to study the effect of various combinations of and relative sequencing of D, P, and Z in cell growth inhibition. A population pharmacokinetic stimulation study was conducted on Z in silico and used together with the growth inhibition data to derive principles for future in vivo use of this drug combination. Results The inhibitory effects of Z on combinations of D and P were sequence dependent. Treatment simultaneously with DPZ or with DP followed by Z (DP,Z) showed synergistic effects in all 3 cell lines. However, sequencing with Z followed by DP (Z,DP), gave an antagonistic effect, suggesting that D and P should be administered when the effect of Z is low. The induction of apoptosis was also sequence dependent. The in silico pharmacokinetic study suggested the feasibility of deriving a 5-day-on/2-day-off regimen for Z, in which D and P administration commences when levels of Z are low, allowing levels of Z to accumulate sufficiently during the remainder of the cycle. Conclusion These data suggests that it is feasible to design clinical trials with these settings to maximize the efficacy of this combined drug regimen. © 2009 Wiley Periodicals, Inc. Head Neck, 2009 [source] In vitro assessment of cytochrome P450 inhibition: Strategies for increasing LC/MS-based assay throughput using a one-point IC50 method and multiplexing high-performance liquid chromatographyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2007Tong Lin Abstract A fast and robust LC/MS-based cytochrome P450 (CYP) inhibition assay, using human liver microsomes, has been fully developed and validated for the major human liver CYPs. Probe substrates were phenacetin, diclofenac, S-mephenytoin, and dextromethorphan for CYP1A2, CYP2C9, CYP2C19, and CYP2D6, respectively. Midazolam and testosterone were chosen for CYP3A4. Furafylline, sulfaphenazole, tranylcypromine, quinidine, and ketoconazole were identified as positive control inhibitors for CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, respectively. To increase the throughput of the assay, a one-point method was developed, using data from CYP inhibition assays conducted at one concentration (i.e., 10 µM), to estimate the drug concentration at which the metabolism of the CYP probe substrate was reduced by 50% (IC50). The IC50 values from the one-point assay were validated by correlating the results with IC50 values that were obtained with a traditional eight-point concentration,response curve. Good correlation was achieved with the slopes of the trendlines between 0.95 and 1.02 and with R2 between 0.77 and 1.0. Throughput was increased twofold by using a Cohesive multiplexing high-performance liquid chromatography system. The one-point IC50 estimate is useful for initial compound screening, while the full concentration,response IC50 method provides detailed CYP inhibition data for later stages of drug development. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 2485,2493, 2007 [source] Modeling the Inhibitor Activity and Relative Binding Affinities in Enzyme-Inhibitor-Protein Systems: Application to Developmental Regulation in a PG-PGIP SystemBIOTECHNOLOGY PROGRESS, Issue 3 2004Wayne W. Fish Within a number of classes of hydrolytic enzymes are certain enzymes whose activity is modulated by a specific inhibitor-protein that binds to the enzyme and forms an inactive complex. One unit of a specific inhibitor-protein activity is often defined as the amount necessary to inhibit one unit of its target enzyme by 50 %. No objective quantitative means is available to determine this point of 50 % inhibition in crude systems such as those encountered during purification. Two models were derived: the first model is based on an irreversible binding approximation, and the second, or equilibrium, model is based on reversible binding. The two models were validated using the inhibition data for the polygalacturonase-polygalacturonase-inhibiting protein (PG-PGIP) system. Theory and experimental results indicate that the first model can be used for inhibitor protein activity determination and the second model can be used for inhibitor protein activity determination as well as for comparison of association constants among enzymes and their inhibitor-proteins from multiple sources. The models were used to identify and further clarify the nature of a differential regulation of expression of polygalacturonase-inhibiting protein in developing cantaloupe fruit. These are the first relations that provide for an objective and quantitative determination of inhibitor-protein activity in both pure and crude systems. Application of these models should prove valuable in gaining insights into regulatory mechanisms and enzyme-inhibitor-protein interactions. [source] Poly- l -proline type II peptide mimics as probes of the active site occupancy requirements of cGMP-dependent protein kinaseCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2005R. Zhang Abstract:, Based on the X-ray crystal structure of cAMP-dependent protein kinase (PKA) with the endogenous inhibitor PKI and the X-ray crystal structure of cyclin-dependent kinase 2 (CDK2) with a substrate peptide, a proposal is put forth that some protein kinases bind peptide substrates in their active sites in the poly- l -proline type II (PPII) conformation. In this work, PPII peptide mimics are evaluated as pseudosubstrate inhibitors of cGMP-dependent protein kinase (PKG) to explore if PKG also binds peptide substrates in the PPII conformation. Inhibition data of our PPII mimetics provide evidence that the P , 1, P , 2, and P , 3 residues of substrate peptides bind in the PPII conformation (, approximately ,75°, , approximately 145°). In addition, the inhibition data also suggest that the P , 1, P , 2, and P , 3 residues in substrate peptides bind with a gauche(,) ,1 angle. [source] Functional Classification of Protein Kinase Binding Sites Using CavbaseCHEMMEDCHEM, Issue 10 2007Daniel Kuhn Dr. Abstract Increasingly, drug-discovery processes focus on complete gene families. Tools for analyzing similarities and differences across protein families are important for the understanding of key functional features of proteins. Herein we present a method for classifying protein families on the basis of the properties of their active sites. We have developed Cavbase, a method for describing and comparing protein binding pockets, and show its application to the functional classification of the binding pockets of the protein family of protein kinases. A diverse set of kinase cavities is mutually compared and analyzed in terms of recurring functional recognition patterns in the active sites. We are able to propose a relevant classification based on the binding motifs in the active sites. The obtained classification provides a novel perspective on functional properties across protein space. The classification of the MAP and the c-Abl kinases is analyzed in detail, showing a clear separation of the respective kinase subfamilies. Remarkable cross-relations among protein kinases are detected, in contrast to sequence-based classifications, which are not able to detect these relations. Furthermore, our classification is able to highlight features important in the optimization of protein kinase inhibitors. Using small-molecule inhibition data we could rationalize cross-reactivities between unrelated kinases which become apparent in the structural comparison of their binding sites. This procedure helps in the identification of other possible kinase targets that behave similarly in "binding pocket space" to the kinase under consideration. [source] | |||||||||||||