Quantitative Site-Specific Chemoproteomic Profiling of Protein Lipoylation.

Protein lipoylation is an evolutionarily conserved post-translational modification from prokaryotes to eukaryotes. Lipoylation is implicated with several human diseases, including metabolic disorders, cancer, and Alzheimer's disease. While individual lipoylated proteins have been biochemically studied, a strategy for globally quantifying lipoylation with site-specific resolution in proteomes is still lacking. Herein, we developed a butyraldehyde-alkynyl probe to specifically label and enrich lipoylations in complexed biological samples. Combined with a chemoproteomic pipeline using customized tandem enzyme digestions and a biotin enrichment tag with enhanced ionization, we successfully quantified all known lipoylation sites in both