Effect of pyrazinamidase activity on pyrazinamide resistance in Mycobacterium tuberculosis

Patricia Sheen, Patricia Ferrer, Robert H. Gilman, Jon López-Llano, Patricia Fuentes, Eddy Valencia, Mirko J. Zimic

Research output: Contribution to journalArticlepeer-review

56 Scopus citations


Resistance of Mycobacterium tuberculosis to pyrazinamide is associated with mutations in the pncA gene, which codes for pyrazinamidase. The association between the enzymatic activity of mutated pyrazinamidases and the level of pyrazinamide resistance remains poorly understood. Twelve M. tuberculosis clinical isolates resistant to pyrazinamide were selected based on Wayne activity and localization of pyrazinamidase mutation. Recombinant pyrazinamidases were expressed and tested for their kinetic parameters (activity, kcat, Km, and efficiency). Pyrazinamide resistance level was measured by Bactec-460TB and 7H9 culture. The linear correlation between the resistance level and the kinetic parameters of the corresponding mutated pyrazinamidase was calculated. The enzymatic activity and efficiency of the mutated pyrazinamidases varied with the site of mutation and ranged widely from low to high levels close to the corresponding of the wild type enzyme. The level of resistance was significantly associated with pyrazinamidase activity and efficiency, but only 27.3% of its statistical variability was explained. Although pyrazinamidase mutations are indeed associated with resistance, the loss of pyrazinamidase activity and efficiency as assessed in the recombinant mutated enzymes is not sufficient to explain a high variability of the level of pyrazinamide resistance, suggesting that complementary mechanisms for pyrazinamide resistance in M. tuberculosis with mutations in pncA are more important than currently thought.

Original languageEnglish (US)
Pages (from-to)109-113
Number of pages5
Issue number2
StatePublished - Mar 2009


  • Enzymatic activity
  • Pyrazinamidase
  • Resistance
  • Tuberculosis
  • pncA

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Microbiology (medical)
  • Infectious Diseases


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