Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bovine liver dihydrofolate reductase has been solubilized in reverse micelles of cationic surfactant cetyltrimethylammonium bromide (CTAB) in isooctane-chloroform (1:1,V/V) mixture. Variation of waterpool (WO), pH and surfactant concentration showed that the enzyme activity was regulated by these parameters and was higher than the activity found in aqueous buffer (defined as superactivity); the maximum being at WO 13.3, pH 7.0 and CTAB concentration 75 mM. The Michaelis constants, Km for the substrate FAH2 and NADPH were found to be greater than those determined in water. Since reverse micelles have some features similar to those of biomembranes, display of super activity by dihydrofolate reductase indicates that enzymes in vivo may possess higher activity than actually observed in vitro studies in aqueous solutions.
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PMID:The phenomenon of super activity in dihydrofolate reductase entrapped inside reverse micelles in apolar solvents. 281 11

A selective and sensitive high-performance liquid chromatographic method was developed for the determination of aditoprim, a new dihydrofolate reductase inhibitor, in the plasma of cows and pigs. The compound and its internal standard were extracted with chloroform from plasma buffered at pH 9 and chromatographed on a muBondapak reversed-phase column with a mixture of acetonitrile and 0.5% ammonium carbonate aqueous solution and detected by UV absorption. Aditoprim can be quantitatively extracted from plasma. The limit for quantitative determination was ca. 0.050 micrograms/ml with a standard deviation of +/- 0.006 micrograms/ml and an accuracy of +/- 3%. The assay was linear over the concentration range 0.1-5.0 micrograms/ml (precision 0.007-0.09 micrograms/ml), and the day-to-day accuracy was better than +/- 3.5%. No interference was observed from either metabolite(s) or coadministered sulphonamides. The new procedure was compared with a microbiological assay by analysing plasma samples from pigs treated with aditoprim. The two methods gave similar results in the range 0.5-5.0 micrograms/ml.
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PMID:Determination of aditoprim, a new dihydrofolate reductase inhibitor, in the plasma of cows and pigs. 381 29