Bioconversion of substituted naphthalenes and ß-eudesmol with the cytochrome P450 BM3 variant F87V.

Bioconversion of various substituted naphthalenes that contain 1-methoxy- and 1-ethoxy-naphthalenes, methylnaphthalenes, dimethylnaphthalenes, and naphthalenecarboxylic acid methyl esters were performed using recombinant Escherichia coli cells, which expressed the gene coding for a cytochrome P450 BM3 variant F87V (P450 BM3 (F87V)) that was N-terminally fused to an archaeal peptidyl-prolyl cis-trans isomerase. In addition, bioconversion experiments with the same substrates were carried out using those that expressed the phnA1A2A3A4 genes for a polycyclic aromatic hydrocarbon (PAH)-dihydroxylating dioxygenase, which originated from a PAH-utilizing marine bacterium Cycloclasticus sp. strain A5. Consequently, a variety of mono-hydroxylated derivatives were generated from these substituted naphthalenes. Oxidative aryl coupling was found to produce a novel compound 4,4'-diethoxy-[2,2']-binaphthalenyl-1,1'-diol from 1-ethoxynaphthalene with the E. coli cells expressing the P450 BM3 (F87V) gene. This recombinant E. coli was further shown to introduce the hydroxyl group regio- and stereo-specifically into a sesquiterpene ß-eudesmol.

Functional expression system for cytochrome P450 genes using the reductase domain of self-sufficient P450RhF from Rhodococcus sp. NCIMB 9784.

Cytochrome P450RhF from Rhodococcus sp. NCIMB 9784 is a self-sufficient P450 monooxygenase. We report here a simple system for the functional expression of various P450 genes using the reductase domain of this P450RhF, which comprises flavin mononucleotide- and nicotinamide adenine dinucleotide phosphate binding motifs and a [2Fe2S] ferredoxin-like center. Vector pRED was constructed, which carried the T7 promoter, cloning sites for a P450, a linker sequence, and the P450RhF reductase domain, in this order. The known P450 genes, encoding P450cam from Pseudomonas putida (CYP101A) and P450bzo from an environmental metagenome library (CYP203A), were expressed on vector pRED as soluble fusion enzymes with their natural spectral features in Escherichia coli. These E. coli cells expressing the P450cam and P450bzo genes could convert (+)-camphor and 4-hydroxybenzoate into 5-exo-hydroxycamphor and protocatechuate (3,4-dihydroxybenzoate), respectively (the expected products). Using this system, we also succeeded in directly identifying the function of P450 CYP153A as alkane 1-monooxygenase for the first time, i.e., E. coli cells expressing a P450 CYP153A gene named P450balk, which was isolated form Alcanivorax borkumensis SK2, converted octane into 1-octanol with high efficiency (800 mg/l). The system presented here may be applicable to the functional identification of a wide variety of bacterial cytochromes P450.

Isolation and functional analysis of cytochrome P450 CYP153A genes from various environments.

The cytochrome P450 CYP153 family is thought to mediate the terminal hydroxylation reactions of n-alkanes. We isolated 16 new P450 CYP153A genes (central region) from various environments such as petroleum-contaminated soil and groundwater, as well as one from the n-alkane-degrading bacterium Alcanivorax borkumensis SK2 (designated P450balk). The sequences of the new P450 genes were extended by PCR to generate full-length chimeric P450 genes, using the N- and C-terminal domains of P450balk. A differential CO-reduced P450 spectral analysis indicated that 8 P450 genes among the 16 chimeric genes were expressed in Escherichia coli to generate a soluble and functional enzyme. The several functional chimeric P450s and P450balk were further fused to the reductase domain of the self-sufficient P450 monooxygenase (P450RhF) at the C-terminus. E. coli cells expressing these self-sufficient P450 chimeric genes converted n-alkanes, cyclohexane, 1-octene, n-butylbenzene, and 4-phenyl-1-butene into 1-alkanols, cyclohexanol, 1,2-epoxyoctane, 1-phenyl-4-butanol, and 2-phenethyl-oxirane, respectively.