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Journal of Bacteriology, May 1999, p. 2752-2758, Vol. 181, No. 9
Department of Chemistry and Biochemistry,
Utah State University, Logan, Utah 84322-0300
Received 30 December 1998/Accepted 24 February 1999
The metabolism of acetone was investigated in the actinomycete
Rhodococcus rhodochrous (formerly Nocardia
corallina) B276. Suspensions of acetone- and isopropanol-grown
R. rhodochrous readily metabolized acetone. In contrast,
R. rhodochrous cells cultured with glucose as the carbon
source lacked the ability to metabolize acetone at the onset of the
assay but gained the ability to do so in a time-dependent fashion.
Chloramphenicol and rifampin prevented the time-dependent increase in
this activity. Acetone metabolism by R. rhodochrous was
CO2 dependent, and 14CO2 fixation
occurred concomitant with this process. A nucleotide-dependent acetone
carboxylase was partially purified from cell extracts of acetone-grown
R. rhodochrous by DEAE-Sepharose chromatography. Analysis
by sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggested
that the acetone carboxylase was composed of three subunits with
apparent molecular masses of 85, 74, and 16 kDa. Acetone metabolism by
the partially purified enzyme was dependent on the presence of a
divalent metal and a nucleoside triphosphate. GTP and ITP supported the
highest rates of acetone carboxylation, while CTP, UTP, and XTP
supported carboxylation at 10 to 50% of these rates. ATP did not
support acetone carboxylation. Acetoacetate was determined to be the
stoichiometric product of acetone carboxylation. The longer-chain
ketones butanone, 2-pentanone, 3-pentanone, and 2-hexanone were
substrates. This work has identified an acetone carboxylase with a
novel nucleotide usage and broader substrate specificity compared to
other such enzymes studied to date. These results strengthen the
proposal that carboxylation is a common strategy used for acetone
catabolism in aerobic acetone-oxidizing bacteria.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Evidence for an Inducible Nucleotide-Dependent
Acetone Carboxylase in Rhodococcus rhodochrous
B276
*
Corresponding author. Mailing address: Department of
Chemistry and Biochemistry, College of Science, Utah State University, 300 University Blvd., Logan, UT 84322-0300. Phone: (435) 797-3969. Fax:
(435) 797-3390. E-mail: ensigns{at}cc.usu.edu.
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