Subcellular localization of leucine aminotransferase and alpha-hydroxyacid dehydrogenase in Trypanosoma cruzi.

Homogenates of Trypanosoma cruzi epimastigotes (Tulahuén strain) show L-leucine aminotransferase activity (EC 2.6.1.6). Subcellular distribution of this enzyme and of alpha-hydroxyacid dehydrogenase, enzymes which share a common substrate/product (alpha-ketoisocaproate), has been studied by means of differential centrifugation, digitonin treatment of entire parasites, isopycnic centrifugation and determination of latency of enzymes in the large granule fraction. The results indicate that both enzymes have a dual localization, in the cytosol and in the mitochondrion, probably in the matrix. On the basis of this location, it is proposed that they operate in a shuttle system transferring reducing equivalents between the cytosol and the mitochondrion.