Activation of aflatoxin B1 by a mono-oxygenase system localized in rat liver mitochondria.

Structurally intact rat liver mitoplasts free of detectable microsomal contamination contain enzymatic activity to metabolize aflatoxin B1 (AFB1). The activated component(s) bind to mitochondrial macromolecules and also inhibit mitochondrial protein synthesis. The activity of intact mitoplasts or sonicated particles is partly dependent on the addition of NADPH-generating system. Under optimal conditions, the mitochondrial enzyme has specific activity of 60 to 65 pmol/mg and represents about 15 to 18% of total cytoplasmic activity for AFB1 activation. The enzyme is localized in the soluble fraction of mitochondrial matrix and appears to be distinctly different from the microsomal activity.