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Appl. Environ. Microbiol., 06 1997, 2232-2239, Vol 63, No. 6
F Beltrametti, AM Marconi, G Bestetti, C Colombo, E Galli, M Ruzzi and E Zennaro
The nucleotide sequence of the 4,377-bp chromosomal region of Pseudomonas
fluorescens ST that codes for the oxidation of styrene to phenylacetic acid
was determined. Four open reading frames, named styA, styB, styC, and styD,
were identified in this region. Sequence analysis and biotransformation
assays, performed with batch and continuous cultures, allowed us to
identify the functions of the sequenced genes. styA and styB encode a
styrene monooxygenase responsible for the transformation of styrene to
epoxystyrene; styC codes for the second enzyme of the pathway, an
epoxystyrene isomerase that converts epoxystyrene to phenylacetaldehyde;
and the styD gene produces a phenylacetaldehyde dehydrogenase that oxidizes
phenylacetaldehyde to phenylacetic acid. StyA, 415-amino-acids long, was
found to be weakly homologous to p-hydroxybenzoate hydroxylase from both P.
fluorescens and P. aeruginosa and to salicylate hydroxylase from P. putida,
suggesting that it might be a flavin adenine dinucleotide-binding
monooxygenase. StyB was found to be partially homologous to the
carboxyterminal part of the 2,4-dichlorophenol-6-monooxygenase encoded by
plasmid pJP4, while the styC product did not share significant homology
with any known proteins. The fourth open reading frame, styD, could encode
a protein of 502 amino acids and was strongly homologous to several
eukaryotic and prokaryotic aldehyde dehydrogenases. The order of the genes
corresponds to that of the catabolic steps. The previously suggested
presence of the gene for epoxystyrene reductase, which directly converts
epoxystyrene to 2-phenylethanol (A.M. Marconi, F. Beltrametti, G. Bestetti,
F. Solinas, M. Ruzzi, E. Galli, and E. Zennaro, Appl. Environ. Microbiol.
61:121-127, 1996), has not been confirmed by sequencing and by
biotransformation assays performed in continuous cultures. A copy of the
insertion sequence ISI162, belonging to the IS21-like family of elements,
was identified immediately downstream of the styrene catabolic genes.
Copyright © 1997, American Society for Microbiology
Sequencing and functional analysis of styrene catabolism genes from Pseudomonas fluorescens ST
Department of Genetics and Biology of Microorganisms, University of Milan, Italy.
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