Risto K Kostiainen

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Electrospray ionization-mass spectrometry (ESI-MS) is a very promising tool for the analysis of phospholipid compositions, but is hampered by the fact that not all molecular species are detected with equal efficiency. We studied this and other issues that need to be taken into account to obtain truly quantitative compositional data. The key findings were as(More)
The initial glucuronidation rates were determined for eight recombinant human UDP-glucuronosyltransferases (UGTs) of the 1A subfamily, and the bisubstrate kinetics and inhibition patterns were analyzed. At low substrate concentrations, the reactions followed general ternary complex kinetics, whereas at higher concentrations of both substrates, the reactions(More)
Losartan, candesartan, and zolarsartan are AT(1) receptor antagonists that inhibit the effect of angiotensin II. We have examined their glucuronidation by liver microsomes from several animals and by recombinant human UDP-glucuronosyltransferases (UGTs). Large differences in the production of different glucuronide regioisomers of the three sartans were(More)
A multidimensional study on the glucuronidation of anabolic androgenic steroids and their phase I metabolites by 11 recombinant human UDP-glucuronosyltransferases (UGTs) was carried out using liquid chromatographic-tandem mass spectrometric analyses. Large differences between the enzymes with respect to the conjugation profiles of the 11 tested aglycones(More)
Eight human liver UDP-glucuronosyltransferases (UGTs) were expressed in baculovirus-infected insect cells as fusion proteins carrying a short C-terminal extension that ends with 6 histidine residues (His tag). The activity of recombinant UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT2B4, UGT2B7, and UGT2B15 was almost fully inhibited by 0.2% Triton X-100. In the case(More)
A liquid chromatographic-electrospray/tandem mass spectrometric (LC-ESI-MS/MS) method was developed for the analysis of dopamine and its phase I and phase II metabolites from brain microdialysis samples. The method provides for the first time the analysis of intact dopamine glucuronide and sulfate without hydrolysis. The paper describes also an enzymatic(More)
Propranolol is a nonselective beta-adrenergic blocker used as a racemic mixture in the treatment of hypertension, cardiac arrhythmias, and angina pectoris. For study of the stereoselective glucuronidation of this drug, the two propranolol glucuronide diastereomers were biosynthesized, purified, and characterized. A screen of 15 recombinant human(More)
The purpose of this work was to identify human UDP-glucuronosyltransferases (UGTs) capable of glucuronidating dopamine. Using a sensitive liquid chromatography-tandem mass spectrometry method, we screened all 19 known human UGTs and found that only one enzyme, UGT1A10, catalyzed dopamine glucuronidation at substantial rates, yielding both(More)
Oligomeric procyanidins were isolated from the leaves and flowers of hawthorn (Crataegus laevigata). A trimer, epicatechin-(4 beta-->8)-epicatechin-(4 beta-->6)-epicatechin, and a pentamer consisting of (-)-epicatechin units linked through C-4 beta/C-8 bonds have been isolated from hawthorn for the first time, in addition to known procyanidins including(More)
Here we used electrospray ionization mass spectrometry for quantitative determination of lipid molecular species in human fibroblasts and their plasma membrane incorporated into enveloped viruses. Both influenza virus selecting ordered domains and vesicular stomatitis virus (VSV) depleted of such domains [Scheiffele, P., et al. (1999) J. Biol. Chem. 274,(More)