Variation of superoxide dismutase levels in extracts of Mycobacterium leprae from armadillo liver.

Recent improvements in the sensitivity of assay methods for superoxide dismutase (SOD) have enabled the detection of this enzyme in 18 cell-free extracts of purified Mycobacterium leprae. By converting back to units of SOD obtained in the cytochrome c-based method previously used in work on this enzyme in mycobacteria, it was shown that extracts of M. leprae had 0.15-3.84 U SOD/mg protein (this study). A mean value of 1.31 U/mg protein was calculated. It was not possible to find any factors which could explain the very high levels in some extracts, although correlation with the period of tissue storage at -80 degrees C suggested that M. leprae in freshly killed tissue would have 1.77 U SOD/mg protein. The possibility of contamination by SODs from host and other organisms was unlikely since on gel electrophoresis extracts of M. leprae with high levels of SOD showed only a single band of activity characteristic of manganese-dependent SOD previously demonstrated.