Nicotinamidase/pyrazinamidase of Mycobacterium tuberculosis forms homo-dimers stabilized by disulfide bonds

Relationship between xanthine oxidase gene polymorphisms and anti-tuberculosis drug-induced liver injury in a Chinese population

This study was designed to investigate the association of the xanthine oxidase (XO) polymorphisms and susceptibility to anti-tuberculosis drug-induced liver injury (ATDILI) in Chinese population. A total of 183 tuberculosis patients were enrolled. Patients with ATDILI were classified as cases and those without ATDILI were classified as controls. Genotyping for XO polymorphisms was determined by polymerase chain reaction and direct sequencing. The allele frequencies and genotype distribution was analyzed using the Chi square test to analyze the association between the gene polymorphisms and ATDILI. Binary logistic regression analysis was performed to assess the risk factors of ATDILI. A total of 21 patients were developed liver injury during anti-tuberculosis treatment in this study, with an incidence of 11.48%. In genotype analysis, no significant difference was observed in the alleles and genotypes frequencies of the six SNPs between two groups (P > 0.05). In haplotype analysis, carriers with GGGATA (rs1884725- rs2295475 -rs45523133- rs206812- rs206813- rs7575607) haplotype had a significantly higher risk of ATDILI compared with other haplotypes (OR = 2.445, 95%CI: 1.058-5.652, P < 0.05). This study suggested that the haplotype GGGATA constructed with rs206812 and rs7575607 mutant alleles might contribute to ATDILI susceptibility in a Chinese population.

Metallochaperones Are Needed for Mycobacterium tuberculosis and Escherichia coli Nicotinamidase-Pyrazinamidase Activity

Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis and remains one of the major causes of disease and death worldwide. Pyrazinamide is a key drug used in the treatment of tuberculosis, yet its mechanism of action is not fully understood, and testing strains of M. tuberculosis for pyrazinamide resistance is not easy with the tools that are presently available. The significance of the present research is that a metallochaperone-like protein may be crucial to pyrazinamide’s mechanisms of action and of resistance. This may support the development of improved tools to detect pyrazinamide resistance, which would have significant implications for the clinical management of patients with tuberculosis: drug regimens that are appropriately tailored to the resistance profile of a patient’s individual strain lead to better clinical outcomes, reduced onward transmission of infection, and reduction of the development of resistant strains that are more challenging and expensive to treat.

Mycobacterium tuberculosis nicotinamidase-pyrazinamidase (PZAse) is a metalloenzyme that catalyzes conversion of nicotinamide-pyrazinamide to nicotinic acid-pyrazinoic acid. This study investigated whether a metallochaperone is required for optimal PZAse activity. M. tuberculosis and Escherichia coli PZAses (PZAse-MT and PZAse-EC, respectively) were inactivated by metal depletion (giving PZAse-MT–Apo and PZAse-EC–Apo). Reactivation with the E. coli metallochaperone ZnuA or Rv2059 (the M. tuberculosis analog) was measured. This was repeated following proteolytic and thermal treatment of ZnuA and Rv2059. The CDC1551 M. tuberculosis reference strain had the Rv2059 coding gene knocked out, and PZA susceptibility and the pyrazinoic acid (POA) efflux rate were measured. ZnuA (200 μM) achieved 65% PZAse-EC–Apo reactivation. Rv2059 (1 μM) and ZnuA (1 μM) achieved 69% and 34.3% PZAse-MT–Apo reactivation, respectively. Proteolytic treatment of ZnuA and Rv2059 and application of three (but not one) thermal shocks to ZnuA significantly reduced the capacity to reactivate PZAse-MT–Apo. An M. tuberculosis Rv2059 knockout strain was Wayne positive and susceptible to PZA and did not have a significantly different POA efflux rate than the reference strain, although a trend toward a lower efflux rate was observed after knockout. The metallochaperone Rv2059 restored the activity of metal-depleted PZAse in vitro. Although Rv2059 is important in vitro, it seems to have a smaller effect on PZA susceptibility in vivo. It may be important to mechanisms of action and resistance to pyrazinamide in M. tuberculosis. Further studies are needed for confirmation.

IMPORTANCE Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis and remains one of the major causes of disease and death worldwide. Pyrazinamide is a key drug used in the treatment of tuberculosis, yet its mechanism of action is not fully understood, and testing strains of M. tuberculosis for pyrazinamide resistance is not easy with the tools that are presently available. The significance of the present research is that a metallochaperone-like protein may be crucial to pyrazinamide’s mechanisms of action and of resistance. This may support the development of improved tools to detect pyrazinamide resistance, which would have significant implications for the clinical management of patients with tuberculosis: drug regimens that are appropriately tailored to the resistance profile of a patient’s individual strain lead to better clinical outcomes, reduced onward transmission of infection, and reduction of the development of resistant strains that are more challenging and expensive to treat.