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Pseudomonad cyclopentadecanone monooxygenase displaying an uncommon spectrum of Baeyer-Villiger oxidations of cyclic ketones.
Iwaki, Hiroaki; Wang, Shaozhao; Grosse, Stephan; Bergeron, Hélène; Nagahashi, Ayako; Lertvorachon, Jittiwud; Yang, Jianzhong; Konishi, Yasuo; Hasegawa, Yoshie; Lau, Peter C K.
Afiliación
  • Iwaki H; National Research Council Canada, Biotechnology Research Institute, 6100 Royalmount Avenue, Montreal, Quebec H4P 2R2, Canada.
Appl Environ Microbiol ; 72(4): 2707-20, 2006 Apr.
Article en En | MEDLINE | ID: mdl-16597975
ABSTRACT
Baeyer-Villiger monooxygenases (BVMOs) are biocatalysts that offer the prospect of high chemo-, regio-, and enantioselectivity in the organic synthesis of lactones or esters from a variety of ketones. In this study, we have cloned, sequenced, and overexpressed in Escherichia coli a new BVMO, cyclopentadecanone monooxygenase (CpdB or CPDMO), originally derived from Pseudomonas sp. strain HI-70. The 601-residue primary structure of CpdB revealed only 29% to 50% sequence identity to those of known BVMOs. A new sequence motif, characterized by a cluster of charged residues, was identified in a subset of BVMO sequences that contain an N-terminal extension of approximately 60 to 147 amino acids. The 64-kDa CPDMO enzyme was purified to apparent homogeneity, providing a specific activity of 3.94 micromol/min/mg protein and a 20% yield. CPDMO is monomeric and NADPH dependent and contains approximately 1 mol flavin adenine dinucleotide per mole of protein. A deletion mutant suggested the importance of the N-terminal 54 amino acids to CPDMO activity. In addition, a Ser261Ala substitution in a Rossmann fold motif resulted in an improved stability and increased affinity of the enzyme towards NADPH compared to the wild-type enzyme (K(m) = 8 microM versus K(m) = 24 microM). Substrate profiling indicated that CPDMO is unusual among known BVMOs in being able to accommodate and oxidize both large and small ring substrates that include C(11) to C(15) ketones, methyl-substituted C(5) and C(6) ketones, and bicyclic ketones, such as decalone and beta-tetralone. CPDMO has the highest affinity (K(m) = 5.8 microM) and the highest catalytic efficiency (k(cat)/K(m) ratio of 7.2 x 10(5) M(-1) s(-1)) toward cyclopentadecanone, hence the Cpd designation. A number of whole-cell biotransformations were carried out, and as a result, CPDMO was found to have an excellent enantioselectivity (E > 200) as well as 99% S-selectivity toward 2-methylcyclohexanone for the production of 7-methyl-2-oxepanone, a potentially valuable chiral building block. Although showing a modest selectivity (E = 5.8), macrolactone formation of 15-hexadecanolide from the kinetic resolution of 2-methylcyclopentadecanone using CPDMO was also demonstrated.
Asunto(s)

Texto completo: 1 Banco de datos: MEDLINE Asunto principal: Pseudomonas / Ácidos Grasos / Oxigenasas de Función Mixta / Cetonas Idioma: En Revista: Appl Environ Microbiol Año: 2006 Tipo del documento: Article País de afiliación: Canadá

Texto completo: 1 Banco de datos: MEDLINE Asunto principal: Pseudomonas / Ácidos Grasos / Oxigenasas de Función Mixta / Cetonas Idioma: En Revista: Appl Environ Microbiol Año: 2006 Tipo del documento: Article País de afiliación: Canadá