The final acylation step in Taxol biosynthesis: Cloning of the taxoid C13-side-chain N-benzoyltransferase from Taxus
AUTOR(ES)
Walker, Kevin
FONTE
The National Academy of Sciences
RESUMO
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,1H-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 kcat ≈ 1.5 ± 0.3 s−1 and Km 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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=123112Documentos Relacionados
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