Journal of Bacteriology, February 1999, p. 1343-1347, Vol. 181, No. 4
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Department of Pharmacology,
Received 9 September 1998/Accepted 3 December 1998
Arylamine N-acetyltransferases (NATs) are found in many
eukaryotic organisms, including humans, and have previously been
identified in the prokaryote Salmonella typhimurium. NATs
from many sources acetylate the antitubercular drug isoniazid and so
inactivate it. nat genes were cloned from
Mycobacterium smegmatis and Mycobacterium tuberculosis, and expressed in Escherichia coli and
M. smegmatis. The induced M. smegmatis NAT
catalyzes the acetylation of isoniazid. A monospecific antiserum raised
against pure NAT from S. typhimurium recognizes NAT from
M. smegmatis and cross-reacts with recombinant NAT from
M. tuberculosis. Overexpression of mycobacterial
nat genes in E. coli results in predominantly
insoluble recombinant protein; however, with M. smegmatis
as the host using the vector pACE-1, NAT proteins from M. tuberculosis and M. smegmatis are soluble. M. smegmatis transformants induced to express the M. tuberculosis nat gene in culture demonstrated a threefold higher resistance to isoniazid. We propose that NAT in mycobacteria could have
a role in acetylating, and hence inactivating, isoniazid.
*
Corresponding author. Mailing address: Department of
Pharmacology, University of Oxford, Mansfield Rd., Oxford OX1 3QT,
United Kingdom. Phone: (44 1865) 271596. Fax: (44 1865) 271853. E-mail: esim{at}worf.molbiol.ox.ac.uk.
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