Exploring a Unique Class II Diterpene Cyclase: The Modified Catalytic Acid Motif Contributes to Ring Contraction in Premutilin Synthase.

The class II diterpene cyclase from pleuromutilin biosynthesis contains a unique variant of the otherwise highly conserved DxDD motif (DxDM), which cooperatively serves as the catalytic acid, and uniquely produces an "A" ring contracted product, mutildienyl pyrophosphate (MPP). The correlation between these features was investigated here via substitution of aspartate for methionine, which largely blocks the production of MPP and leads to a novel hydroxylated product, syn-halima-13E-en-5β-ol-15-PP, providing insight into this unique reaction.