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 reaction is the acetylation of 10-deacetylbaccatin-III (10-DAB) to baccatin-III, an assumed precursor of taxol. Here we describe the cell foe acetylation of IO-DAB in crude extracts from roots of Taxus baccata saplings 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 radiolabeled baccatin-III: was confirmed by co-chromatography of the labeled product with authentic baccatin-III in different TLC-systems and HPLC. Furthermore, the acetylation product showed an identical UV spectrum as authentic baccatin-III. Crude extracts from cambium of stems yielded three- to fivefold lower activity. This is in agreement with our finding that the taxol titer in roots was considerably higher than that in cambium. (C) 1996 Academic Press, Inc.