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J. Bacteriol., Jun 1995, 3095-3103, Vol 177, No. 11
E Kim and GJ Zylstra
Beijerinckia sp. strain B1 is able to grow on either biphenyl or m- xylene
as the sole source of carbon and is capable of cooxidizing many polycyclic
aromatic hydrocarbons. The catabolic pathways for biphenyl and m-xylene
degradation are coinduced and share common downstream enzymatic reactions.
The catabolic pathway for biphenyl degradation involves two meta-cleavage
steps, one for 2,3-dihydroxybiphenyl and a second for catechol. The
catabolic pathway for m-xylene involves one m- cleavage step for
3-methylcatechol. The genes for two meta-cleavage dioxygenases were cloned
from Beijerinckia sp. strain B1 on a single fragment of genomic DNA. The
two genes are located approximately 5.5 kb away from one another.
Expression of each gene separately in Escherichia coli and analysis of the
meta-cleavage dioxygenase produced showed that one enzyme was more specific
for 2,3-dihydroxybiphenyl while the second was more specific for catechol.
The genes for the two meta-cleavage enzymes were thus labeled bphC and xylE
for 2,3- dihydroxybiphenyl 1,2-dioxygenase and catechol 2,3-dioxygenase,
respectively. Nondenaturing polyacrylamide gel electrophoresis followed by
enzyme activity staining showed that the two meta-cleavage dioxygenases
could be easily separated from each other. Similar analyses of Beijerinckia
sp. strain B1 grown on succinate, biphenyl, or m-xylene indicate that both
meta-cleavage enzymes are induced when cells are grown on either biphenyl
or m-xylene. The nucleotide sequence was determined for both bphC and xylE.
The two genes are transcribed in opposite directions, demonstrating that at
least two operons must be involved in biphenyl degradation by Beijerinckia
sp. strain B1.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Molecular and biochemical characterization of two meta-cleavage dioxygenases involved in biphenyl and m-xylene degradation by Beijerinckia sp. strain B1
Center for Agricultural Molecular Biology, Cook College, Rutgers University, New Brunswick, New Jersey 08903-0231, USA.
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