Title page Simultaneous Absolute Protein Quantification of Carboxylesterases 1 and 2 in Human Liver Tissue Fractions using Liquid Chromatography Tandem Mass Spectrometry

Abstract

Abstract The aims of this study were to develop a robust method for simultaneous quantification of carboxylesterases (CESs) 1 and 2 and to quantify those absolute protein levels in human liver tissue fractions. Unique peptide fragments of CES1 and CES2 in tryptically digested human liver microsomes (HLMs) and cytosol (HLC) were simultaneously quantified by liquid chromatography equipped with tandem mass spectrometry (LC-MS/MS) using corresponding stable isotope-labeled peptides as internal standards. Bovine serum albumin was used as a blank matrix for the calibration curve samples. Our procedure showed good digestion efficiency, sensitivity, linearity of calibration curve, and reproducibility. The protein levels of CES1 an