ABSTRACT

The increasing popularity of protein-based therapeutics and biomaterials calls for efficient, mild, and site-selective protein reactions. Enlightened by the reactivity of o-quinone, in this work, we reported a chemoenzymatic photoreaction of tyrosine by coupling tyrosinase oxidation and visible-light-induced photoaddition. The tyrosinase selectively oxidizes accessible tyrosines in a peptide or a protein to o-quinone; under visible light, o-quinone reacts with electron-rich alkenes (e.g., vinyl ethers) to give [3+2] photoaddition products with high stability and fast kinetics in aqueous buffer solutions in a one-pot reaction. Ascribable to the substrate specificity of the tyrosinase, this reaction preferentially labels terminal or highly accessible tyrosines. Engineering a tripeptide GGY (called “Y-tag”) at the C-terminus of proteins provided such an accessible tyrosine, and allowed for rapid and site-selective protein labeling. Combined with a deglycosylation step, a single tyrosine residue of Trastuzumab (a clinically used immunoglobulin antibody) was labeled without perturbance of the Her2 protein binding capability.

Reference:

1. Takuwa, A. Sumikawa, M. Chemistry Letters, 1989, 18, 9-12.