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《Nucleosides, nucleotides & nucleic acids》2013,32(5-8):1567-1570
Abstract Dissociation constants and stoichiometry of binding for interaction of trimeric calf spleen purine nucleoside phosphorylase with potent multisubstrate analogue inhibitors were studied by kinetic and spectrofluorimetric methods. 相似文献
2.
Many contaminated sites commonly have complex mixtures of polycyclic aromatic hydrocarbons (PAHs) whose individual microbial
biodegradation may be altered in mixtures. Biodegradation kinetics for fluorene, naphthalene, 1,5-dimethylnaphthalene and
1-methylfluorene were evaluated in sole substrate, binary and ternary systems using Sphingomonas paucimobilis EPA505. The first order rate constants for fluorene, naphthalene, 1,5-dimethylnaphthalene, and 1-methylfluorene were comparable;
yet Monod parameters were significantly different for the tested PAHs. S. paucimobilis completely degraded all the components in binary and ternary mixtures; however, the initial degradation rates of individual
components decreased in the presence of competitive PAHs. Results from the mixture experiments indicate competitive interactions,
demonstrated mathematically. The generated model appropriately predicted the biodegradation kinetics in mixtures using parameter
estimates from the sole substrate experiments, validating the hypothesis of a common rate-determining step. Biodegradation
kinetics in mixtures were affected by the affinity coefficients of the co-occurring PAHs and mixture composition. Experiments
with equal concentrations of substrates demonstrated the effect of concentration on competitive inhibition. Ternary experiments
with naphthalene, 1,5-dimethylnaphthalene and 1-methylfluorene revealed delayed degradation, where depletion of naphthalene
and 1,5-dimethylnapthalene occurred rapidly only after the complete removal of 1-methylfluorene. The substrate interactions
observed in mixtures require a multisubstrate model to account for simultaneous degradation of substrates. PAH contaminated
sites are far more complex than even ternary mixtures; however these studies clearly demonstrate the effect that interactions
can have on individual chemical kinetics. Consequently, predicting natural or enhanced degradation of PAHs cannot be based
on single compound kinetics as this assumption would likely overestimate the rate of disappearance. 相似文献
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《Nucleosides, nucleotides & nucleic acids》2013,32(5-8):1699-1702
Abstract The crystal structure at 2.05 Å resolution of calf spleen PNP complexed with stoichiometric concentration of acyclic nucleoside phosphonate inhibitor, 2,6-diamino-(S)-9-[2-(phosphonomethoxy)propyl]purine, in a new space group P212121 which contains two full trimers in the asymmetric crystal unit is described. 相似文献
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Lipases and esterases are hydrolytic enzymes and are known to hydrolyze esters with unique substrate specificity and acyl chain length selectivity. We have developed a simple competitive multiple substrate assay for determination of acyl chain length selectivity of lipases/esterases using RP-HPLC with UV detection. A method for separation and quantification of 4-nitrophenyl fatty acid esters (C4–C18) was developed and validated. The chain length selectivity of five lipases and two esterases was determined in a multisubstrate reaction system containing equimolar concentrations of 4-nitrophenyl esters (C4–C18). This assay is simple, reproducible, and a useful tool for determining chain length selectivity of lipases/esterases. 相似文献
5.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(6):1291-1318
In drug discovery, different methods exist to create new inhibitors possessing satisfactory biological activity. The multisubstrate adduct inhibitor (MAI) approach is one of these methods, which consists of a covalent combination between analogs of the substrate and the cofactor or of the multiple substrates used by the target enzyme. Adopted as the first line of investigation for many enzymes, this method has brought insights into the enzymatic mechanism, structure, and inhibitory requirements. In this review, the MAI approach, applied to different classes of enzyme, is reported from the point of view of biological activity. 相似文献
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