Enzyme-Dependent Lysine Deprotonation in EZH2 Catalysis

Protein lysine methyltransferases(PKMTs) are key players in epigenetic regulation and have been associated with a variety of diseases, including cancers. The catalytic subunit of Polycomb Repressive Complex 2, EZH2(EC 2.1.1.43), is a PKMT and a member of a familyof SET domain lysine methyltransferasesthat catalyze the transfer of a methyl group from S-adenosyl-l-methionine to lysine27 of histone 3 (H3K27). Wild-type (WT) EZH2primarily catalyzes the mono- and dimethylation of H3K27; however, a clinically relevant active site mutation (Y641F) has been shown to alter the reaction specificity, dominantly catalyzing trimethylation of H3K27, and has been linked to tumor genesis and maintenance. Herein, we explore the chemical mechanism of methyl transfer by EZH2and its Y641F mutant with pH–rate profiles and solvent kinetic isotope effects(sKIEs) using a short peptide derived from histone H3[H3(21–44)]. A key component of the chemical reaction is the essential deprotonation of the e-NH3+ group of lysine...