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.