Extracellular enzyme activities potentially involved in the pathogenicity of Mycobacterium tuberculosis.
To evaluate the potential contribution of extracellular enzymes to the pathogenicity of mycobacteria, the presence of selected enzyme activities was investigated in the culture filtrates of the obligate human pathogen Mycobacterium tuberculosis, M. bovis BCG, the opportunistic pathogens M. kansasii and M. fortuitum, and the non-pathogenic species M. phlei and M. smegmatis. For M. tuberculosis and M. bovis, 22 enzyme activities were detected in the culture filtrates and/or cell surfaces, of which eight were absent from the culture fluids of non-pathogens: alanine dehydrogenase, glutamine synthetase, nicotinamidase, isonicotinamidase, superoxide dismutase, catalase, peroxidase and alcohol dehydrogenase. These activities, which correspond to secreted enzymes, formed a significant part (up to 92%) of the total enzyme activities of the bacteria and were absent from the culture fluids and the cell surfaces of the non-pathogenic species M. smegmatis and M. phlei. The extracellular location of superoxide dismutase and glutamine synthetase seemed to be restricted to the obligate pathogens examined. The difference in the enzyme profiles was not attributable to the growth rates of the two groups of bacteria. The presence of the eight enzyme activities in the outermost compartments of obligate pathogens and their absence in those of non-pathogens provides further evidence that these enzymes may be involved in the pathogenicity of mycobacteria. In addition, the eight enzyme activities were demonstrated in the cell extract of M. smegmatis. Stepwise erosion of the cell surface of M. smegmatis to expose internal capsular constituents showed that the various enzyme activities, with the possible exception of superoxide dismutase, were located more deeply in the cell envelope of this bacterium. This suggests that the molecular architecture of the mycobacterial envelopes may play an important role in the pathogenicity of these organisms.
Raynaud
Catherine
C
Institut de Pharmacologie et de Biologie Structurale du CNRS & Université Paul Sabatier, 205 route de Narbonne, 31077 Toulouse cedex, France.
Etienne
Gilles
G
Institut de Pharmacologie et de Biologie Structurale du CNRS & Université Paul Sabatier, 205 route de Narbonne, 31077 Toulouse cedex, France.
Peyron
Pascale
P
Institut de Pharmacologie et de Biologie Structurale du CNRS & Université Paul Sabatier, 205 route de Narbonne, 31077 Toulouse cedex, France.
Lanéelle
Marie-Antoinette
MA
Institut de Pharmacologie et de Biologie Structurale du CNRS & Université Paul Sabatier, 205 route de Narbonne, 31077 Toulouse cedex, France.
Daffé
Mamadou
M
Institut de Pharmacologie et de Biologie Structurale du CNRS & Université Paul Sabatier, 205 route de Narbonne, 31077 Toulouse cedex, France.
D016667:Bacterial Capsules / Q000032:analysis / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000032:analysis*; D004798:Enzymes / Q000032:analysis* / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis* / Q000378:metabolism; D009161:Mycobacterium / Q000201:enzymology* / Q000378:metabolism / Q000472:pathogenicity; D009163:Mycobacterium bovis / Q000201:enzymology / Q000378:metabolism / Q000472:pathogenicity; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000378:metabolism / Q000472:pathogenicity; D009170:Nontuberculous Mycobacteria / Q000201:enzymology / Q000378:metabolism / Q000472:pathogenicity
D017077:Culture Media, Conditioned; D004798:Enzymes; D008565:Membrane Proteins