Mitochondrial Electron Transport Enzymes in Normal and Leukemic Human Leukocytes

Assays of TD transhydrogenase and succinate cytochrome C reductase carried out on the homogenate of normal and leukemic human leukocytes and on the 1.5 M. fraction (fraction 3) of a continuous sucrose density gradient analysis of a crude mitochondrial fraction, provided strong evidence for the mitochondrial location of TD transhydrogenase. A slightly higher activity of these enzymes was found in the homogenate of cells from chronic lymphocytic and acute leukemia compared to those of normal polymorphonuclear leukocytes, normal lymphocytes, and cells from chronic myeloid leukemia. These differences were very much more marked when purified mitochondrial fractions from these cells were examined. The significance of these findings is discussed.