18O2-labeling in quantitative proteomic strategies: a status report.

Enzyme-catalyzed 18O2-labeling offers a universal strategy for uniform labeling of all peptides from any kind of proteins, including post-translationally modified proteins. It is applicable to clinical samples with unrivaled sensitivity. This review discusses strengths and limitations, and advocates the separation of proteolysis from the labeling step. Continued advances in software will facilitate widespread use of enzyme-catalyzed 18O2-labeling to determine changes in protein abundances.