Figure 7.

Nucleophilic activation pathways for the second half-reaction (6*OH denotes the mycolated hydroxy of TMM). A, direct activation of the 6′-hydroxy of TMM for the second half-reaction by His²⁶⁰, stabilized by the β-hydroxy of MA. B, indirect activation scheme proceeding through a proton transfer from the β-hydroxy of MA to His²⁶⁰ followed by the proton transfer from the 6′-hydroxy to deprotonated β-hydroxy of MA.