Characterization of activity and expression of isocitrate lyase in Mycobacterium avium and Mycobacterium tuberculosis.
Analysis by two-dimensional gel electrophoresis revealed that Mycobacterium avium expresses several proteins unique to an intracellular infection. One abundant protein with an apparent molecular mass of 50 kDa was isolated, and the N-terminal sequence was determined. It matches a sequence in the M. tuberculosis database (Sanger) with similarity to the enzyme isocitrate lyase of both Corynebacterium glutamicum and Rhodococcus fascians. Only marginal similarity was observed between this open reading frame (ORF) (termed icl) and a second distinct ORF (named aceA) which exhibits a low similarity to other isocitrate lyases. Both ORFs can be found as distinct genes in the various mycobacterial databases recently published. Isocitrate lyase is a key enzyme in the glyoxylate cycle and is essential as an anapleurotic enzyme for growth on acetate and certain fatty acids as carbon source. In this study we express and purify Icl, as well as AceA proteins, and show that both exhibit isocitrate lyase activity. Various known inhibitors for isocitrate lyase were effective. Furthermore, we present evidence that in both M. avium and M. tuberculosis the production and activity of the isocitrate lyase is enhanced under minimal growth conditions when supplemented with acetate or palmitate.
Höner Zu Bentrup
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Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. boenerk@borcim.wustl.edu
Miczak
A
A
Swenson
D L
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Russell
D G
DG
D000085:Acetates / Q000378:metabolism; D001426:Bacterial Proteins; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006863:Hydrogen-Ion Concentration; D007522:Isocitrate Lyase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D009162:Mycobacterium avium / Q000201:enzymology*; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D016366:Open Reading Frames; D010168:Palmitates / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D019802:Succinic Acid / Q000378:metabolism
D000085:Acetates; D001426:Bacterial Proteins; D007527:Isoenzymes; D010168:Palmitates; D011994:Recombinant Proteins; D019802:Succinic Acid; C402427:icl protein, Mycobacterium; D007522:Isocitrate Lyase