A 10-O-deacetylbaccatin III 10-O-acetyltransferase
biocatalyst from Taxus plants was expressed in bacteria whole-cells that were fed 10-O-deacetylbaccatin III and
cyclopropane carboxylic acid. Product analysis by qualitative LC/ESI-MS suggested that the C10-acylated products
baccatin III, 10-O-n-propionyl-10-O-deacetylbaccatin III, and 10-O-cyclopropanecarbonyl-10-O-deacetylbaccatin III were made in vivo. The results implied that the cells provided non-natural cyclopropanecarbonyl
CoA, from a broad-specificity
CoA ligase, and natural products,
acetyl CoA and n-
propionyl CoA, from reserves in the bacteria for use by
acyltransferase to acylate 10-O-deacetylbaccatin III in vivo. The 10-acyl-10-O-deacetylbaccatin III are precursors used to synthesize new-generation
paclitaxel analogs
SB-T-1214 and SB-T-121303, which are effective against
cancer cells resistant to
paclitaxel and its
drug derivatives. The kcat and KM of the
acyltransferase for cyclopropanecarbonyl
CoA (0.83 s-1, 0.15 M) and n-
propionyl CoA (1.2 s-1, 0.15 M) guided scale-up efforts. The 10-acyl-10-O-deacetylbaccatin III analogs (∼45 mg each) were made in vitro by the
acyltransferase when incubated with the commercial
taxane 10-O-deacetylbaccatin III and synthesized cyclopropanecarbonyl or n-
propionyl CoA. The structures of the 10-acyl products were verified by NMR analyses that confirmed C10 acylation of the
taxane substrate. LC/ESI-MS/MS analysis also supported the identities of the biocatalyzed products. This effort provides a biocatalysis framework to produce new-generation
taxane precursors.