RESUMEN
Discovery of the CYP107Z subfamily of cytochrome P450 oxidases (CYPs) led to an alternative biocatalytic synthesis of 4''-oxo-avermectin, a key intermediate for the commercial production of the semisynthetic insecticide emamectin. However, under industrial process conditions, these wild-type CYPs showed lower yields due to side product formation. Molecular evolution employing GeneReassembly was used to improve the regiospecificity of these enzymes by a combination of random mutagenesis, protein structure-guided site-directed mutagenesis, and recombination of multiple natural and synthetic CYP107Z gene fragments. To assess the specificity of CYP mutants, a miniaturized, whole-cell biocatalytic reaction system that allowed high-throughput screening of large numbers of variants was developed. In an iterative process consisting of four successive rounds of GeneReassembly evolution, enzyme variants with significantly improved specificity for the production of 4''-oxo-avermectin were identified; these variants could be employed for a more economical industrial biocatalytic process to manufacture emamectin.
Asunto(s)
Sistema Enzimático del Citocromo P-450/genética , Sistema Enzimático del Citocromo P-450/metabolismo , Evolución Molecular Dirigida , Insecticidas/metabolismo , Ivermectina/análogos & derivados , Biotransformación , Disacáridos/metabolismo , Biblioteca de Genes , Genes Bacterianos , Ivermectina/metabolismo , Datos de Secuencia Molecular , Mutación , Oxidación-Reducción , Streptomyces/enzimología , Streptomyces/genética , Especificidad por SustratoRESUMEN
4"-Oxo-avermectin is a key intermediate in the manufacture of the agriculturally important insecticide emamectin benzoate from the natural product avermectin. Seventeen biocatalytically active Streptomyces strains with the ability to oxidize avermectin to 4"-oxo-avermectin in a regioselective manner have been discovered in a screen of 3,334 microorganisms. The enzymes responsible for this oxidation reaction in these biocatalytically active strains were found to be cytochrome P450 monooxygenases (CYPs) and were termed Ema1 to Ema17. The genes for Ema1 to Ema17 have been cloned, sequenced, and compared to reveal a new subfamily of CYPs. Ema1 to Ema16 have been overexpressed in Escherichia coli and purified as His-tagged recombinant proteins, and their basic enzyme kinetic parameters have been determined.
Asunto(s)
Sistema Enzimático del Citocromo P-450/genética , Ivermectina/análogos & derivados , Streptomyces/clasificación , Streptomyces/enzimología , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Sistema Enzimático del Citocromo P-450/química , Sistema Enzimático del Citocromo P-450/metabolismo , Ivermectina/química , Ivermectina/metabolismo , Cinética , Datos de Secuencia Molecular , Oxidación-Reducción , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alineación de Secuencia , Análisis de Secuencia de ADN , Estereoisomerismo , Streptomyces/genéticaRESUMEN
The cytochrome P450 monooxygenase Ema1 from Streptomyces tubercidicus R-922 and its homologs from closely related Streptomyces strains are able to catalyze the regioselective oxidation of avermectin into 4"-oxo-avermectin, a key intermediate in the manufacture of the agriculturally important insecticide emamectin benzoate (V. Jungmann, I. Molnár, P. E. Hammer, D. S. Hill, R. Zirkle, T. G. Buckel, D. Buckel, J. M. Ligon, and J. P. Pachlatko, Appl. Environ. Microbiol. 71:6968-6976, 2005). The gene for Ema1 has been expressed in Streptomyces lividans, Streptomyces avermitilis, and solvent-tolerant Pseudomonas putida strains using different promoters and vectors to provide biocatalytically competent cells. Replacing the extremely rare TTA codon with the more frequent CTG codon to encode Leu4 in Ema1 increased the biocatalytic activities of S. lividans strains producing this enzyme. Ferredoxins and ferredoxin reductases were also cloned from Streptomyces coelicolor and biocatalytic Streptomyces strains and tested in ema1 coexpression systems to optimize the electron transport towards Ema1.
Asunto(s)
Sistema Enzimático del Citocromo P-450/metabolismo , Ivermectina/análogos & derivados , Pseudomonas putida/enzimología , Streptomyces/enzimología , Streptomyces/genética , Secuencia de Aminoácidos , Sistema Enzimático del Citocromo P-450/genética , Disacáridos/química , Disacáridos/metabolismo , Ferredoxinas/genética , Ferredoxinas/metabolismo , Regulación Bacteriana de la Expresión Génica , Ingeniería Genética/métodos , Microbiología Industrial/métodos , Ivermectina/química , Ivermectina/metabolismo , Oxidación-Reducción , Oxidorreductasas/genética , Oxidorreductasas/metabolismo , Regiones Promotoras Genéticas , Pseudomonas putida/genética , Pseudomonas putida/crecimiento & desarrollo , Alineación de Secuencia , Streptomyces/clasificación , Streptomyces/crecimiento & desarrollo , Transformación BacterianaRESUMEN
2-Hexyl-5-propylresorcinol is the predominant analog of several dialkylresorcinols produced by Pseudomonas aurantiaca (Pseudomonas fluorescens BL915). We isolated and characterized three biosynthetic genes that encode an acyl carrier protein, a beta-ketoacyl-acyl carrier protein synthase III, and a protein of unknown function, all of which collectively allow heterologous production of 2-hexyl-5-propylresorcinol in Escherichia coli. Two regulatory genes exhibiting similarity to members of the AraC family of transcriptional regulators are also present in the identified gene cluster. Based on the deduced functions of the proteins encoded by the gene cluster and the observed incorporation of labeled carbons from octanoic acid into 2-hexyl-5-propylresorcinol, we propose that dialkylresorcinols are derived from medium-chain-length fatty acids by an unusual head-to-head condensation of beta-ketoacyl thioester intermediates. Genomic evidence suggests that there is a similar pathway for the biosynthesis of the flexirubin-type pigments in certain bacteria belonging to the order Cytophagales.
