A simple graphical method was described for determining the kinetic parameters of substrate inhibition of complete and partial types. The method consists of plotting experimental data as [Formula: see text] versus the reciprocals of the substrate concentrations, where V max represents the maximal velocity. The reaction rate constant of enzyme-substrate-inhibitor complex [Formula: see text] can ...

Kinetic studies of the cleavage of dehydroepiandrosterone-sulfate (i) and androstenediol-3-sulfate by a particulate enzyme preparation from a rat testicular microsomal fraction gave K m values of 2.04 x 10-6M for DHA-S and 0.935 x 10-6M for androstenediol-3-sulfate with identical Vma x values° Inhibition studies with equimolar concentrations of substrate and inhibitor demonstrated that 5~-andro...

1. A theoretical appraisal of the alternative pathway mechanism for a two-substrate enzyme shows that this mechanism is capable of giving rise to apparent substrate inhibition or substrate activation (Dalziel, 1958). It has now been shown that these phenomena may occur simultaneously in the following ways. With certain relationships between the kinetic parameters and the constant concentration ...

Predicting the magnitude of potential drug-drug interactions is important for underwriting patient safety in the clinical setting. Substrate-dependent inhibition of cytochrome P450 enzymes may confound extrapolation of in vitro results to the in vivo situation. However, the potential for substrate-dependent inhibition with CYP2D6 has not been well characterized. The inhibition profiles of 20 kn...

Renal transporter-mediated drug-drug interactions (DDIs) are of significant clinical concern, as they can adversely impact drug disposition, efficacy, and toxicity. Emerging evidence suggests that human renal organic cation transporter 2 (hOCT2) and multidrug and toxin extrusion proteins 1 and 2-K (hMATE1/2-K) exhibit substrate-dependent inhibition, but their impact on renal drug secretion and ...

The RecQ helicases constitute a small but highly conserved helicase family. Proteins in this family are of particular interest because they are critical to maintenance of genomic stability in prokaryotes and eukaryotes. Eukaryotic RecQ helicase family members have been shown to unwind not only DNA duplexes but also DNAs with alternative structures, including structures stabilized by G quartets ...

Four unresolved issues of cyclin-dependent kinase (CDK) regulation have been addressed by structural studies this year - the mechanism of CDK inhibition by members of the INK4 family of CDK inhibitors, consensus substrate sequence recognition by CDKs, the role of the cyclin subunit in substrate recognition and the structural mechanism underlying CDK inhibition by phosphorylation.

background: in this study, the inhibition rate of different oil concentrations containing pcbs (1242 and 1254 pcb arochlors) on the anaerobic biomass was investigated by specific methanogenic activity using the vials with volume of 120 ml. methods: original samples were divided into two groups: with soil containing pcbs and without pcbs and the control samples in both cases were just contained ...