Overexpression and mechanistic analysis of chromosomally encoded aminoglycoside 2′-N-acetyltransferase (AAC(2′)-Ic) from Mycobacterium tuberculosis

被引:69
作者
Hegde, SS [1 ]
Javid-Majd, F [1 ]
Blanchard, JS [1 ]
机构
[1] Yeshiva Univ Albert Einstein Coll Med, Dept Biochem, Bronx, NY 10461 USA
关键词
D O I
10.1074/jbc.M108810200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The chromosomally encoded aminoglycoside N-acetyltransferase, AAC(2')-Ic, of Mycobacterium tuberculosis has a yet unidentified physiological function. The aac(2')-Ic gene was cloned and expressed in Escherichia coli, and AAC(2')-Ic was purified. Recombinant AAC(2')-Ic was a soluble protein of 20,000 Da and acetylated all aminoglycosides substrates tested in vitro, including therapeutically important antibiotics. Acetyl-CoA was the preferred acyl donor. The enzyme, in addition to acetylating aminoglycosides containing 2'-amino substituents, also acetylated kanamycin A and amikacin that contain a 2'-hydroxyl substituent, although with lower activity, indicating the capacity of the enzyme to perform both N-acetyl and O-acetyl transfer. The enzyme exhibited "substrate activation" with many aminoglycoside substrates while exhibiting Michaelis-Menten kinetics with others. Kinetic studies supported a random kinetic mechanism for AAC(2')-Ic. Comparison of the kinetic parameters of different aminoglycosides suggested that their hexopyranosyl residues and, to a lesser extent, the central aminocyclitol residue carry the major determinants of substrate affinity.
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页码:45876 / 45881
页数:6
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