areABC genes determine
the catabolism of aryl esters in Acinetobacter sp. ADP1.
Rheinallt M. Jones, Lauren S. Collier, Ellen
L. Neidle and Peter A. Williams.
J.Bacteriol. (1999) 181:4568-4575.
ABSTRACT
Acinetobacter sp. strain ADP1 is able to grow on a range of esters
of aromatic alcohols, converting them to the corresponding aromatic
carboxylic acids by the sequential action of three inducible enzymes:
an areA-encoded esterase, an areB-encoded benzyl alcohol
dehydrogenase, and an areC-encoded benzaldehyde dehydrogenase.
The are genes, adjacent to each other on the chromosome and
transcribed in the order areCBA, were located 3.5 kbp upstream
of benK. benK, encoding a permease implicated in benzoate uptake,
is at
one end of the ben-cat supraoperonic cluster for benzoate catabolism
by the beta-ketoadipate pathway. Two open reading frames which may
encode a transcriptional regulator, areR, and a porin, benP,
separate benK from areC. Each are gene was individually expressed
to high specific activity in Escherichia coli. The relative activities
against different substrates of the cloned enzymes were, within experimental
error, identical to that of wild-type Acinetobacter sp. strain
ADP1 grown on either benzyl acetate, benzyl alcohol, or 4-hydroxybenzyl
alcohol
as the carbon source. The substrate preferences of all three enzymes
were broad, encompassing a range of substituted aromatic compounds
and in the case of the AreA esterase, different carboxylic acids. The
areA, areB, and areC genes were individually disrupted on
the
chromosome by insertion of a kanamycin resistance cassette, and the
rates at which the resultant strains utilized substrates of the aryl ester
catabolic pathway were severely reduced as determined by growth competitions
between the mutant and wild-type strains.