I studied the kinetics and sensitivity toward inhibition by levamisole and R 8231 of the most important human alkaline phosphatase isoenzymes. N-Ethylaminoethanol proved superior to the now widely used diethanolamine buffer, especially for the enzymes from the intestine and placenta, behaving as an uncompetitive activator. The optimum pH largely depends on the substrate concentration. The addit...

This paper presents a simple solution to the problem of approximating the calculated curve of reaction progress to the measured curve which is usually disturbed by initial oscillation of auxiliary lactate dehydrogenase (LDH) reaction. The experiments leading to the determination of the apparent Km for phosphoenolpyruvate (PEP) and Vm were performed. For precise estimation of kinetic parameters ...

We investigated the effects of retinoic acids on mitochondrial permeability transition (MPT) measured as changes in rhodamine 123 fluorescence from both isolated heart mitochondria and HeLa cells. We report that all-trans-retinoic acid (atRA), 9-cis-retinoic acid, and 13-cis-retinoic acid induce a drop in mitochondrial membrane potential in isolated mitochondria. The atRA effect was done throug...

Cigarette smoke is a complex mixture containing, among other chemicals, pyridine alkaloids and N-nitrosamines. Carcinogenic tobacco-specific N-nitrosamines, N-nitrosodimethylamine (NDMA) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), are both activated by cytochrome P450 (CYP) 2E1 in rats. Previous reports indicate that nicotine and the main nicotine metabolite, cotinine, reduce the ...

in this study, the interaction of various concentrations of cadmium sulfate with peroxidase (e.c 1.11.1.7) was investigated in different temperatures (25-35 °c). for this purpose thermostability, spectrophotometry, spectroflorimetry and kinetics studies were done to obtain thermodynamic parameters including ∆g°, ∆h°m, ∆s°m, tm and also kinetics parameters including vmax and km. the results show...

A micro-reactor system with continual spectrophotometric detection has been operated in Sequential Injection lab-on-valve (SI-LOV) mode and applied to enzyme kinetics and inhibition studies, using acetylcholinesterase (AChE) and angiotensin-converting enzyme (ACE) as model systems. With the advantages of automation, real-time kinetic measurement, and thorough mixing, the SI-LOV micro-reactor sy...

In this study, the authors investigated the anti-melanogenic effects of 3,8-dihydroxyquinoline (jineol) isolated from Scolopendra subspinipes mutilans, the mechanisms responsible for its inhibition of melanogenesis in melan-a cells, and its antioxidant efficacy. Mushroom tyrosinase activities and melanin contents were determined in melan-a cells, and the protein and mRNA levels of MITF, tyrosin...

Phosphoglycerate dehydrogenase was purified from extracts of Escherichia coli by conventional methods and the enzyme was crystallized from ammonium sulfate solution. The crystalline preparation appeared homogenous in the ultracentrifuge and upon zone electrophoresis. The reduction of hydroxypyruvate-P proceeded faster than the oxidation of phosphoglycerate (PGA) and the latter reaction was inhi...

The selective estrogen receptor modulator, raloxifene, has been demonstrated as a potent uncompetitive inhibitor of human liver aldehyde oxidase-catalyzed oxidation of phthalazine, vanillin, and nicotine-Delta1'(5')-iminium ion, with K(i) values of 0.87 to 1.4 nM. Inhibition was not time-dependent. Raloxifene has also been shown to be a noncompetitive inhibitor of an aldehyde oxidase-catalyzed ...

Thymidine kinase activity in rat C6 glioma cells is inhibited by 50 to 70% after 4 hr incubation with 20 mM D-glucosamine. The inhibition is uncompetitive with respect to thymidine, reducing both the apparent Km and Vmax of the enzyme. The inhibition does not appear to be caused by the reversible combination of the enzyme with a cytoplasmic inhibitor, including D-glucosamine and its metabolites...