Characterizing Two Cytochrome P450s in Tiacumicin Biosynthesis Reveals Reaction Timing for Tailoring Modifications.

Functions of the tailoring enzymes for the biosynthesis of tiacumicin B (1) have been previously determined. However, the reaction timing remains elusive. Herein, we report the in vitro biochemical characterization of two P450 enzymes TiaP1 and TiaP2. The investigation of their substrate scope and kinetic parameters clearly demonstrates that the TiaP2-catalyzed C-20 hydroxylation is the first tailoring step and the TiaP1-catalyzed C-18 hydroxylation is the last step in the biosynthesis of 1.