Publications

• Preliminary assessment of the C13-side chain 2'-hydroxylase involved in taxol biosynthesis.

  Long R.M., Croteau R.

  The biosynthesis of the anticancer drug Taxol in yew (Taxus) species is thought to involve the preliminary formation of the advanced taxane diterpenoid intermediate baccatin III upon which the functionally important N-benzoyl phenylisoserinoyl side chain is subsequently assembled at the C13-O-posi ... >> More

  The biosynthesis of the anticancer drug Taxol in yew (Taxus) species is thought to involve the preliminary formation of the advanced taxane diterpenoid intermediate baccatin III upon which the functionally important N-benzoyl phenylisoserinoyl side chain is subsequently assembled at the C13-O-position. In vivo feeding studies with Taxus tissues and characterization of the two transferases responsible for C13-side chain construction have suggested a sequential process in which an aminomutase converts alpha-phenylalanine to beta-phenylalanine which is then activated to the corresponding CoA ester and transferred to baccatin III to yield beta-phenylalanoyl baccatin III (i.e., N-debenzoyl-2'-deoxytaxol) that undergoes subsequent 2'-hydroxylation and N-benzoylation to afford Taxol. However, because the side chain transferase can utilize both beta-phenylalanoyl CoA and phenylisoserinoyl CoA in the C13-O-esterification of baccatin III, ambiguity remained as to whether the 2'-hydroxylation step occurs before or after transfer of the amino phenylpropanoyl moiety. Using cell-free enzyme systems from Taxus suspension cells, no evidence was found for the direct hydroxylation of beta-phenylalanine to phenylisoserine; however, microsomal preparations from this tissue appeared capable of the cytochrome P450-mediated hydroxylation of beta-phenylalanoyl baccatin III to phenylisoserinoyl baccatin III (i.e., N-debenzoyltaxol) as the penultimate step in the formation of Taxol and related N-substituted taxoids. These preliminary results, which are consistent with the proposed side chain assembly process, have clarified an important step of Taxol biosynthesis and set the foundation for cloning the responsible cytochrome P450 hydroxylase gene. << Less

  Biochem Biophys Res Commun 338:410-417(2005) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• The final acylation step in taxol biosynthesis: cloning of the taxoid C13-side-chain N-benzoyltransferase from Taxus.

  Walker K., Long R., Croteau R.B.

  The formation of several acyl groups and an amide group of Taxol is catalyzed by regioselective CoA thioester-dependent acyltransferases. Several full-length acyltransferase sequences, obtained from a cDNA library constructed from mRNA isolated from Taxus cuspidata cells induced for Taxol producti ... >> More

  The formation of several acyl groups and an amide group of Taxol is catalyzed by regioselective CoA thioester-dependent acyltransferases. Several full-length acyltransferase sequences, obtained from a cDNA library constructed from mRNA isolated from Taxus cuspidata cells induced for Taxol production with methyl jasmonate, were individually expressed in Escherichia coli, from which a cDNA clone encoding a 3'-N-debenzoyl-2'-deoxytaxol N-benzoyltransferase was identified. This recombinant enzyme catalyzes the stereoselective coupling of the surrogate substrate N-debenzoyl-(3'RS)-2'-deoxytaxol with benzoyl-CoA to form predominantly one 3'-epimer of 2'-deoxytaxol. The product 2'-deoxytaxol was confirmed by radio-HPLC,(1)H-NMR, and chemical ionization-MS. This enzymatic reaction constitutes the final acylation in the Taxol biosynthetic pathway. The full-length cDNA coding for the N-benzoyltransferase has an ORF of 1,323 nucleotides and encodes a 441-residue protein with a calculated molecular weight of 49,040. The recombinant enzyme expressed in E. coli has a pH optimum at 8.0, a k(cat) approximately 1.5 +/-0.3 s(-1) and K(m) values of 0.42 mM and 0.40 mM for the N-deacylated taxoid and benzoyl-CoA, respectively. In addition to improving the production yields of Taxol in genetically engineered host systems, this enzyme provides a means of attaching modified aroyl groups to taxoid precursors for the purpose of improving drug efficacy. << Less

  Proc. Natl. Acad. Sci. U.S.A. 99:9166-9171(2002) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Molecular cloning and heterologous expression of the C-13 phenylpropanoid side chain-CoA acyltransferase that functions in Taxol biosynthesis.

  Walker K., Fujisaki S., Long R., Croteau R.

  The structural pharmacophore of Taxol, responsible for binding the N terminus of the beta-subunit of tubulin to arrest cell proliferation, comprises, in part, the 13-O-(N-benzoyl-3-phenylisoserinoyl) side chain. To identify the side chain transferase of Taxol biosynthesis, a set of transacylases o ... >> More

  The structural pharmacophore of Taxol, responsible for binding the N terminus of the beta-subunit of tubulin to arrest cell proliferation, comprises, in part, the 13-O-(N-benzoyl-3-phenylisoserinoyl) side chain. To identify the side chain transferase of Taxol biosynthesis, a set of transacylases obtained from an enriched cDNA library (constructed from mRNA isolated from Taxus cuspidata cells induced with methyl jasmonate for Taxol production) was screened. A cDNA clone (designated TAX7) encoding a taxoid C-13 O-phenylpropanoyltransferase was isolated which yielded a recombinant enzyme that catalyzes the selective 13-O-acylation of baccatin III with beta-phenylalanoyl CoA as the acyl donor to form N-debenzoyl-2'-deoxytaxol. This enzymatic product was converted to 2'-deoxytaxol by chemical N-benzoylation, and the identity of this derivative was confirmed by spectrometric analyses. The full-length cDNA has an ORF of 1,335 bases and encodes a 445-aa protein with a calculated molecular weight of 50,546. Evaluation of kinetic parameters revealed K(m) values of 2.4 +/-0.5 microM and 4.9 +/-0.3 microM for baccatin III and beta-phenylalanoyl-CoA, respectively. The pH optimum for the recombinant O-(3-amino-3-phenylpropanoyl)transferase is at 6.8. Identification of this clone completes acquisition of the five aroyl/acyltransferases involved in the biosynthesis of Taxol. Application of these transacylase genes in suitable host cells can improve the production yields of Taxol and could enable the preparation of second-generation Taxol analogs possessing greater bioactivity and improved water solubility. << Less

  Proc. Natl. Acad. Sci. U.S.A. 99:12715-12720(2002) [PubMed] [EuropePMC]