Enantioselective in-line and off-line CE methods for the kinetic study on cimetidine and its chiral metabolites with reference to flavin-containing monooxygenase genetic isoforms

Electrophoresis. 2009 Apr;30(7):1248-57. doi: 10.1002/elps.200800604.


An in-line screening and an off-line chiral CE method were developed to determine the stereoselectivity of flavin-containing monooxygenase (FMO) isoforms using cimetidine (CIM) as a substrate. The S-oxygenation of CIM was investigated using achiral chemical oxidants and (human supersomes) enzymatic metabolism procedures. In the off-line setup, the chiral selector sulfobutylether-beta-CD was chosen to separate the CIM S-oxide (CSO) metabolites. The electrophoretic migration order of CSO was confirmed to be (+) before (-) through the use of single enantiomers obtained by preparative chromatography. For the electrophoretically mediated microanalysis method, the in-line enzymatic reaction was performed in 100 mM phosphate reaction buffer (pH 8.3), whereas 50 mM phosphate buffer with 30 mM chiral selector (pH 2.5) was used as a BGE. During the screening of FMO isoenzymes by the electrophoretically mediated microanalysis method, formation of the new chiral center on the CIM sulfur was found to be stereoselective. FMO1 produces more (-)-CSO-enantiomer, while FMO3 generates mainly (+)-CSO-enantiomer. On the other hand, FMO5 shows no activity. The kinetic constants of FMO1 and FMO3 were measured by the off-line method. A K(m)=4.31 mM for the formation of the (+)-CSO-enantiomer and a K(m)=4.56 mM for the (-)-CSO-enantiomer are reported for the first time for FMO1.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Calibration
  • Chromatography, High Pressure Liquid / methods
  • Cimetidine / analogs & derivatives*
  • Cimetidine / analysis*
  • Cimetidine / chemical synthesis
  • Cimetidine / metabolism
  • Deoxycholic Acid / chemistry
  • Electrophoresis, Capillary / instrumentation
  • Electrophoresis, Capillary / methods*
  • Kinetics
  • Oxygenases / metabolism*
  • Protein Isoforms / metabolism
  • Stereoisomerism
  • Substrate Specificity


  • Protein Isoforms
  • Deoxycholic Acid
  • Cimetidine
  • Oxygenases
  • dimethylaniline monooxygenase (N-oxide forming)
  • cimetidine sulfoxide