Assuming complete hepatic substrate metabolism and system linearity, quantitative effects of in vivo competitive inhibition are investigated. Following oral administration of a substrate in the presence of a competitive inhibitor, determination of the inhibition constant (Ki) is possible when plasma concentration-time profiles of both substrate and inhibitor are available. When triazolam is the...

The concentration of an inhibitor that decreases the rate of an enzyme-catalysed reaction by 50%, symbolized i(0.5), is often used in pharmacological studies to characterize inhibitors. It can be estimated from the common inhibition plots used in biochemistry by means of the fact that the extrapolated inhibitor concentration at which the rate becomes infinite is equal to -i(0.5). This method is...

Rat skeletal-muscle hexokinase was partially purified by ammonium sulphate fractionation and gel filtration. The mechanism of the skeletal-muscle hexokinase was studied kinetically by initial-velocity analysis and product inhibition. Glucose 6-phosphate was a non-competitive inhibitor of glucose and ATP. ADP was a non-competitive inhibitor of glucose and a competitive inhibitor of ATP. The data...

abstract kinetic properties of root of peroxidase of gundelia tournefortii investigated at different ph, temperature and different inhibitors. maximum activity of peroxidase achieved at ph 5.5-6 in according to type of substrate. activity of peroxidase increased at constant concentration of h2o2 and different concentration of guaiacol, catechol and pyrogallol. the maximum activity in presence o...

1. Inhibition of the pyrophosphatase and orthophosphatase activities of human liver and small-intestinal alkaline-phosphatase preparations by different classes of inhibitors has been studied. 2. Each type of substrate, pyrophosphate or orthophosphate, is a competitive inhibitor of hydrolysis of the other type. 3. l-Phenylalanine is a non-competitive inhibitor of both types of activity of the in...

The kinetic properties of 50,000-fold purified cultured human T lymphoblast (MOLT-4) deoxycytidine kinase were examined. The reaction velocity had an absolute requirement for magnesium. Maximal activity was observed at pH 6.5-7.0 with Mg:ATP for 1:l. High concentrations of free Mg2+ or free ATP were inhibitory. Double reciprocal plots of initial velocity studies yielded intersecting lines for b...