katGI and katGII encode two different catalases-peroxidases in Mycobacterium fortuitum

Abstract

It has been suggested that catalase-peroxidase plays an important role in several aspects of mycobacterial metabolism and is a virulence factor in the main pathogenic mycobacteria. In this investigation, we studied genes encoding for this protein in the fast-growing opportunistic pathogen Mycobacterium fortuitum. Nucleotide sequences of two different catalase-peroxidase genes (katGI and katGII) of M. fortuitum are described. They show only 64% homology at the nucleotide level and 55% identity at the amino acid level, and they are more similar to catalases-peroxidases from different bacteria, including mycobacteria, than to each other. Both proteins were found to be expressed in actively growing M. fortuitum, and both could also be expressed when transformed into Escherichia coli and M. aurum. We detected the presence of a copy of IS6100 in the neighboring region of a katG gene in the M. fortuitum strain in which this element was identified (strain FC1). The influence of each katG gene on isoniazid (isonicotinic acid hydrazide; INH) susceptibility of mycobacteria was checked by using the INH-sensitive M. aurum as the host. Resistance to INH was induced when katGI was transformed into INH-sensitive M. aurum, suggesting that this enzyme contributes to the natural resistance of M. fortuitum to the drug. This is the first report showing two different genes encoding same enzyme activity which are actively expressed within the same mycobacterial strain.Mycobacterium is an old bacterial genus which includes species from a broad range of ecological niches (14). Pathogenicity ranges from strict specificity for humans or animals, such as Mycobacterium tuberculosis, M. leprae, or M. paratuberculosis, to specificity for saprophytes, such as M. smegmatis and M. phlei. Occupying an intermediate position is M. fortuitum, which can be isolated from clinical samples as an opportunistic pathogen and from environmental sources as a saprophyte (38).The level of adaptation that bacteria have to their environment is possibly related to the number of genes that they are able to activate as a consequence of detection of changes in its environment. The genomic length of the intracellular restricted mycobacterium M. leprae is smaller than that of other mycobacteria (6,11,28). This possibly indicates that M. leprae requires fewer genes for survival within its host due to the stability of its environment.Mycobacteria are considered archetypical intracellular pathogens because of their capacity to invade and multiply within macrophages, and they have evolved mechanisms for evading macrophage-mediated killing. An important mechanism employed by macrophages is the production of toxic reactive oxygen intermediates (5, 27). Catalases-peroxidases are enzymes which are used by bacteria to protect themselves against reactive oxygen intermediates, and hence they are likely to be important for survival within macrophages (27).Catalase-peroxidase plays a crucial enzymatic role in mycobacterial metabolism by increasing the chance of survival inside mac...

Detection and purification of a catalase-peroxidase from Mycobacterium sp. Pyr-1

“…The highest amount of catalase-peroxidase per cell was observed when the cells were in the exponential phase of growth, which is consistent with the ¢nding that the lethal e¡ects of isoniazid lie in the mycolic acid biosynthetic pathway [6]. Similar to the M. tuberculosis T-catalase, which also has a peroxidase-like function, the catalase-peroxidase was heat-labile [5]. Similar to the recombinant catalaseperoxidase of M. tuberculosis [9], the puri¢ed enzyme corresponded to the catalase band and reacted with isoniazid and H P O P to produce radical products that could reduce NBT to a purple formazan product.…”

“…The recombinant catalase-peroxidase from M. tuberculosis [3] and a catalase-peroxidase from Mycobacterium smegmatis [4] have been puri¢ed. Menendez et al [5] suggested that to understand the role of this enzyme in drug activation and antibiotic resistance in pathogenic Mycobacterium spp., the characterization of catalase-peroxidases from other mycobacterial species with di¡erent susceptibilities to isoniazid was needed.…”

Actinobacterial Peroxidases: an Unexplored Resource for Biocatalysis

“…Various mycobacterial catalase-peroxidases (KatG) have been described: Menéndez et al [64] described the two catalase-peroxidases (KatG I and KatG II) produced by Mycobacterium fortuitum, Rafii et al [65] isolated and purified the catalase-peroxidase of a non-pathogenic fast-growing Mycobacterium sp. Pyr-1 and Ro et al [66] purified a catalase-peroxidase from Mycobacterium sp.…”

Regulation of the furA and catC Operon, Encoding a Ferric Uptake Regulator Homologue and Catalase-Peroxidase, Respectively, in Streptomyces coelicolor A3(2)

“…Mycobacteria display varied distribution of catalases among different species. Only HPI-type catalase-peroxidase is detected in Mycobacterium tuberculosis (KatG) (20) and Mycobacterium fortuitum (KatGI and KatGII) (29), whereas some species produce only HPII-type catalase and others produce both types (30,37). Research on mycobacterial catalases has been focused mainly on the role of KatG in conferring susceptibility to isoniazid (INH), an antituberculosis drug.…”