Patent ID: 7544518

Claim:
A method for identifying one or more enzymes in one or more samples containing mixtures of enzymes which comprises the steps: (a) providing affinity tagged protein reactive reagents wherein the reagents have the formula: A-L-PRG where A is an affinity label that selectively binds to a capture reagent, L is a linker group in which one or more atoms is differentially labeled with one or more stable isotopes and PRG is a protein reactive group that is a substrate for an enzyme, wherein an affinity tagged protein reactive reagent is provided for each enzyme that is to be detected and identified in each sample by differentially labeling the linker group of the affinity tagged protein reactive reagent with one or more stable isotopes; (b) reacting each sample with the protein reactive reagents to provide affinity tagged differentially labeled enzyme products in each sample; (c) capturing any affinity tagged differentially labeled enzyme products in the samples using the capture reagent that selectively binds A; (d) releasing captured affinity tagged differentially labeled enzyme products from the capture reagent by disrupting the interaction between the affinity tagged differentially labeled enzyme products and the capture reagent; and (e) detecting and identifying the released affinity tagged differentially labeled enzyme products by mass spectrometry to thereby identify one or more enzymes in the one or more samples.