Macrolactonization to 10-deoxymethynolide catalyzed by the recombinant thioesterase of the picromycin/methymycin polyketide synthase

The recombinant thioesterase (TE) domain of the picromycin/methymycin synthase (PICS) catalyzes the macrolactonization of 3, the N-acetylcysteamine thioester of seco-10-deoxymethynolide to generate 10-deoxymethynolide (1) with high efficiency. By contrast, 4, the 7-dihydro derivative of seco-thioester 3, undergoes exclusive hydrolysis by PICS TE to seco-acid 5. The recombinant TE domain of 6-deoxyerythronolide B synthase (DEBS TE) shows the same reaction specificity as PICS TE, but with significantly lower activity.