(623am) Method for Using Peptide Labeling In Metabolic Flux Analysis

Isotope labeling-based metabolic flux analysis estimates internal metabolic fluxes by fitting predicted labeling patterns to experimental labeling data. Labeling data can be acquired through isotope discriminating techniques such as Nuclear Magnetic Resonance (NMR) spectroscopy or Mass Spectrometry (MS). The relative isotopomer distributions of metabolites can be calculated directly for a given set of flux values and substrate label using the EMU framework. Most of such labeling measurements are derived from amino acids recovered from protein hydrolysates. Here we present a method to directly use complete peptides instead. The aim of this new approach is to retain the compartmental and temporal information associated with each peptide. Because the mass isotopomer distribution (MID) of each peptide is produced by the Cauchy Product of the MIDs of its individual amino acids, the MID of a peptide can be readily determined.