BIOSYNTHESIS OF TAXOL - ENZYMATIC ACETYLATION OF 10-DEACETYLBACCATIN-III TO BACCATIN-III IN CRUDE EXTRACTS FROM ROOTS OF TAXUS-BACCATA

The biosynthesis of taxol is a multistep process. One intermediate rea ction is the acetylation of 10-deacetylbaccatin-III (10-DAB) to baccat in-III, an assumed precursor of taxol. Here we describe the cell foe a cetylation of IO-DAB in crude extracts from roots of Taxus baccata sap lings using C-14- or H-3-labeled acetyl-coenzyme A as the acetyl donor . The reaction is strictly dependent on the addition of 10-DAB and is specific for the 10-hydroxyl group of the taxane ring. Formation of ra diolabeled baccatin-III: was confirmed by co-chromatography of the lab eled product with authentic baccatin-III in different TLC-systems and HPLC. Furthermore, the acetylation product showed an identical UV spec trum as authentic baccatin-III. Crude extracts from cambium of stems y ielded three- to fivefold lower activity. This is in agreement with ou r finding that the taxol titer in roots was considerably higher than t hat in cambium. (C) 1996 Academic Press, Inc.