To evaluate the effects of contractions on the kinetics of uptake and oxidation of palmitate in a physiological muscle preparation, rat hindquarters were perfused with glucose (6 mmol/l), albumin-bound [1-14C]palmitate, and varying amounts of albumin-bound palmitate (200-2,200 micro mol/l) at rest and during muscle contractions. When plotted against the unbound palmitate concentration, palmitat...

1. The enzyme kinetics of dextromethorphan O-demethylation in liver microsomes from three extensive metabolisers (EM) with respect to CYP2D6 indicated high (Km1 2.2-9.4 microM) and low (Km2 55.5-307.3 microM) affinity sites whereas microsomes from two poor metabolisers (PM) indicated a single site (Km 560 and 157 microM). Similar differences were shown for 3-methoxymorphinan O-demethylation to ...

The kinetics of activation of normal and gamma-carboxyglutamic acid (Gla)-deficient prothrombins isolated from cattle maintained for extended periods on the vitamin K antagonist dicoumarol were studied. The catalyst was prothrombinase, comprising isolated Factor Xa, Factor Va, phospholipid vesicles, and calcium ion. The Km and kcat values for prothrombins with 0, 1, 2, 5, 7, and 10 Gla residues...

Understanding the kinetics of Zn absorption by roots and its effect on morphology this organ is relevant for improving crop management, but still poorly studied common beans. Therefore, an experiment was conducted in a hydroponic system with five initial concentrations (CZnI): 0.0; 1.0; 4.0; 16.0 48.0 µmol L-1. The installed plants at V3 stage development aliquots solution collected over 24 h. ...

UDP-glucuronyl transferase (UDPGT) activity was determined for androgens in tissue minces and microsomal fractions from the liver and extrahepatic tissues (kidney, skin, prostate, and preputial glands) of the male rat. Liver microsomes showed the highest UDPGT activity with each of the androgens tested (Vmax = 7, 3, and 10 nmol/minute/mg protein for testosterone, androsterone, and androstanedio...

objective(s): investigation of acute effect on cellular bioenergetics provides the opportunity to characterize the possible adverse effects of drugs more comprehensively. this study aimed to investigate the changes in biochemical and biophysical properties of heart mitochondria induced by captopril and nifedipine antihypertensive treatment. materials and methods: male, 12-week-old wistar rats i...

Nearly 100 years ago Michaelis and Menten published their now classic paper [Michaelis, L., and Menten, M. L. (1913) Die Kinetik der Invertinwirkung. Biochem. Z. 49, 333-369] in which they showed that the rate of an enzyme-catalyzed reaction is proportional to the concentration of the enzyme-substrate complex predicted by the Michaelis-Menten equation. Because the original text was written in G...

In the present study, we conducted a retrospective analysis of 343 in vitro experiments to ascertain whether observed (experimentally determined) values of Ki for reversible cytochrome P450 (P450) inhibition could be reliably predicted by dividing the corresponding IC50 values by two, based on the relationship (for competitive inhibition) in which Ki = IC50/2 when [S] (substrate concentration) ...

Studies were performed to investigate the UDP-glucuronosyltransferase enzyme(s) responsible for the human liver microsomal N2-glucuronidation of the anticonvulsant drug lamotrigine (LTG) and the mechanistic basis for the LTG-valproic acid (VPA) interaction in vivo. LTG N2-glucuronidation by microsomes from five livers exhibited atypical kinetics, best described by a model comprising the express...

Pomegranate-seed residue (PSR) was used in a new strategy for the simultaneous production of Yarrowia lipolytica lipase by submerged fermentation and its immobilization adsorption. This biocatalyst—the fermented solid containing adsorbed (fermPSR)—was evaluated hydrolysis reactions structured lipid synthesis. In shake flasks, yeast extract urea were best nitrogen sources with PSR their use incr...