Three lipases targeted using MS
Three lipases were selected as HCP targets for PRM analysis. They are lipoprotein lipase (LPL), putative phospholipase B-like 2 (PLBL-2), and lysosomal phospholipase A2 isomer X1 (LPLA2). For each lipase, at least three unique tryptic peptide sequences were selected for analysis. The PRM LC-MS instrument setting was similar to the DDA analysis, but the LC gradient was shortened to 80 min. The MS2 signal responses were analyzed by Skyline 4.1 software (MacCoss Lab, University of Washington) where four fragment ions were extracted for each peptide. The PRM quantification was based on the signal intensities comparison to the standard lipase proteins.