SUPEROXIDE-DISMUTASE ACTIVITY OF MYCOBACTERIUM-AVIUM COMPLEX (MAC) STRAINS ISOLATED FROM AIDS PATIENTS

Objective: To explore whether Mycobacterium avium complex (MAC) strain s isolated from AIDS patients produce and secrete superoxide dismutase (SOD). Design: SOD was assayed in the crude extracts and in cell-free medium of 18 MAC strains (MAC 101, LR and SK strains) isolated from A IDS patients to determine intracellular and extracellular activity. Th e SODs were characterized by PAGE and by their sensitivity to azide, c yanide and hydrogen peroxide. Results: SOD activity was detected in ce ll extracts as well as in extracellular medium of all AIDS-MAC strains . PAGE demonstrated a single activity band for each strain, though the re were differences in mobility. All LR strains demonstrated an activi ty band with R(f) = 0.30, while SOD band for MAC 101 and for SK strain s migrated further (R(f) = 0.87). The differences in mobility correlat ed with differences in sensitivity to NaN3 and H2O2. The SOD activity of LR strains was irreversibly inhibited 100% by 5 mM H2O2, and exhibi ted greater sensitivity to NaN3, suggesting the presence of iron in th e enzyme. The SOD activity of SK strains and MAC 101, however, was not inhibited by 5 mM H2O2 but was inhibited to a lesser extent by NaN3, which is characteristic of a manganese-containing SOD. Conclusion: Our data indicate that MAC strains are rich in manganese- or iron-contain ing SOD, which could contribute to the organism's resistance to the ox idative burst of activated macrophages. The secretion of SOD may play an important role in the pathogenesis of MAC strains.