Azo-and nitro-reductase activities and cytochromes of Axcaris lumbricoides var suum and Moniezia expansa.

1. Isoelectric focusing failed to separate the azo- and nitro-reductases in enzyme preparations from either the nematode Ascaris lumbricoides var suum or the cestode Moniezia expansa. The isoelectric point of the reductases from A. lumbricoides var suum was 4-75, and that of the reductases from M. expansa, 4-50. 2. Cytochromes P-450 and b5 were not detected in the 100 000 g pellet of tissue homogenates from either A. lumbricoides var suum of M. expansa. These cytochromes were not induced in either helminth by 20-methylcholanthrene or 1,2-benzanthracene. 3. The absence of cytochromes P-450 and b5 from A. lumbricoides var suum and M. expansa may be the reason for their inability to metabolize drugs by oxidative pathways and for the 100 000 g pellets of their tissue homogenates being unable to reduce azo- or nitro-compounds.