Title

Authors

Affiliation

¹Unidad de Bioinformática y Biología Molecular, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia; ²Department of International Health, Bloomberg School of Public Health, The Johns Hopkins University

Email

mzimic@jhsph.edu; *Corresponding author

Phone

(511) 483-2942

Fax

(511) 483-2942

Article Type

Hypothesis

Date

Received June 22, 2011; Accepted June 28, 2011; Published July 19, 2011

The pncA gene codes the pyrazinamidase of Mycobacterium tuberculosis, which converts pyrazinamide to ammonia and pyrazinoic-acid, the active anti-tuberculous compound. Pyrazinamidase mutations are associated to pyrazinamide-resistant phenotype, however how mutations affect the structure of the pyrazinamidase, and how structural changes affect the enzymatic function and the level of pyrazinamide-resistance is unknown. The structures of mutated pyrazinamidases from twelve Mycobacterium tuberculosis strains and the pyrazinamide-susceptible H37Rv reference strain were modelled using homology modelling and single amino acid replacement. Physical-chemical and structural parameters of each pyrazinamidase were calculated. These parameters were: The change of electrical charge of the mutated amino acid, the change of volume of the mutated amino acid, the change of a special amino acid, the distance of the mutated amino acid to the active site, the distance of the mutated amino acid to the metal-coordination site, and the orientation of the side-chain of the mutated amino acid. The variability of the enzymatic activity of the recombinant pyrazinamidases, and the microbiological susceptibility to pyrazinamide determined by BACTEC 460TB, were modelled in multiple linear regressions. Physical-chemical and structural parameters of the mutated pyrazinamidases were tested as predictors. Structural and physical-chemical variations of the pyrazinamidase explained 75% of the variability of the enzymatic activity, 87% of the variability of the kinetic constant and 40% of the variability of the pyrazinamide-resistance level. Based on computer models of mutated pyrazinamidases, the structural parameters explained a high variability of the enzymatic function, and to a lesser extent the resistance level.

Citation

Quiliano et al. Bioinformation 6(9): 335-339 (2011)
 

Edited by

P Kangueane

ISSN

0973-2063

Publisher

Biomedical Informatics

License

This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. This is distributed under the terms of the Creative Commons Attribution License.