Profiling a taxol pathway 10β-acetyltransferase:: Assessment of the specificity and the production of baccatin III by in vivo acetylation in E-coli

The 10 beta-acetyltransferase on the biosynthetic pathway of the antineoplastic drug Taxol catalyzes the regiospecific transfer of the acetyl group of acetylcoenzyme A (CoA) to 10-deacetylbaccatin Ill. We demonstrate that in addition to acetyl group transfer, the overexpressed enzyme also catalyzes the exchange of propionyl and n-butyryl from the corresponding CoA thioester to the hydroxyl group at C10 of the co-substrate. Also, in vivo studies revealed that E. coli, producing endogenous acetyl-CoA and overexpressing the recombinant acetyltransferase, can convert exogenously supplied 10-deacetylbaccatin Ill to baccatin Ill. Potentially, this heterologous in vivo production method in bacteria could be optimized to couple various unnatural acyl-CoA analogs to myriad amino and/or hydroxyl acceptors by acyltransferase catalysis; conceivably, this process could facilitate the preparation of second-generation Taxols.