Mechanism of isoniazid uptake in Mycobacterium tuberculosis.
Initial transport kinetics of isoniazid (INH) and its uptake at the plateau were studied in Mycobacterium tuberculosis H37Rv under various experimental conditions. The initial uptake velocity increased linearly with INH concentration from 2 x 10(-6) M to 10(-2) M. It was modified neither by addition of a protonophore that abolished proline transport, nor following ATP depletion by arsenate, which inhibited glycerol uptake, two transport processes taken as controls for secondary active transport and facilitated diffusion, respectively. Microaerobiosis or low temperature (4 degrees C) were without effect on initial uptake. It is thus likely that INH transport in M. tuberculosis proceeds by a passive diffusion mechanism, and that catalase-peroxidase (KatG) is not involved in the actual transport. However, conditions inhibiting KatG activity (high INH concentration, microaerobiosis, low temperature) decrease cell radioactivity at the uptake plateau. It is proposed that INH transport occurs by passive diffusion. KatG is involved only in the intracellular accumulation of oxidized derivatives of INH, especially of isonicotinic acid, which is trapped inside cells in its ionized form. This model explains observed and previously known characteristics of the accumulation of radioactivity in the presence of [14C]INH for various species and strains of mycobacteria.
Institut de Pharmacologie et de Biologie Structurale du CNRS and Université Paul Sabatier205 route de Narbonne, 31077 Toulouse cedexFrance.
Fabienne
F
Bardou
Institut de Pharmacologie et de Biologie Structurale du CNRS and Université Paul Sabatier205 route de Narbonne, 31077 Toulouse cedexFrance.
Catherine
C
Raynaud
Institut de Pharmacologie et de Biologie Structurale du CNRS and Université Paul Sabatier205 route de Narbonne, 31077 Toulouse cedexFrance.
Corinne
C
Ramos
Institut de Pharmacologie et de Biologie Structurale du CNRS and Université Paul Sabatier205 route de Narbonne, 31077 Toulouse cedexFrance.
Marie Antoinette
MA
Lanéelle
Institut de Pharmacologie et de Biologie Structurale du CNRS and Université Paul Sabatier205 route de Narbonne, 31077 Toulouse cedexFrance.
Gilbert
G
Lanŕelle
D000995:Antitubercular Agents / Q000493:pharmacokinetics*; D001149:Arsenates / Q000494:pharmacology; D001426:Bacterial Proteins; D001693:Biological Transport, Active / Q000187:drug effects; D002250:Carbon Radioisotopes; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D004058:Diffusion; D007476:Ionophores / Q000494:pharmacology; D007538:Isoniazid / Q000493:pharmacokinetics*; D007700:Kinetics; D008954:Models, Biological; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism; D013696:Temperature
D000995:Antitubercular Agents; D001149:Arsenates; D001426:Bacterial Proteins; D002250:Carbon Radioisotopes; D007476:Ionophores; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D010544:Peroxidases; C076136:catalase HPI; C025657:arsenic acid; D007538:Isoniazid