Covalent bond formation between natural amino acid residues and small molecules (chemical modification of proteins) is a fundamental technology for developing biopharmaceuticals and biomaterials and has been actively studied in recent years. It has been reported that tyrosine residues are involved in signal transduction through phosphorylation and are abundant at the interface of protein-protein interactions. From the viewpoint of elucidating biological phenomena, a technology to selectively and efficiently modify tyrosine residues is expected to be a chemical tool that will contribute to life science research.
We focused on the oxygen (O2)-driven oxidase laccase and developed a novel tyrosine modification reaction1,2. In this technique, laccase oxidizes 1-methyl-4-arylurazole (MAUra)3, a labeling reagent, to modify tyrosine residues efficiently (k = 7.9 × 104 M-1∙s-1). This reaction does not require the addition of an oxidant, and the reaction is driven by O2 dissolved in an aqueous solution, thus minimizing oxidative side reactions on other amino acid residues. We have comprehensively labeled tyrosine residues on proteins in cell lysate. We performed the profiling of the labeled proteins by enriching them at the level of peptide fragments and detecting them by nanoLC-MS/MS to analyze the state and environment of the tyrosine residues.