Translated from Biokhimiia 25(6) 1081-1084. 1960. Amino acid synthesis from keto acids and ammonia has been followed up in the microsome-containing supernatant fraction obtained by differential centrifugation of a rat kidney. Partition of these fractions by starch electrophoresis showed that amino acid synthesis from pyruvic acid is most rapid in fractions migrating towards the anode. In the same zone glutamic dehydrogenase, which catalyses synthesis of glutamic acid from a-ketoglutaric acid, showed its highest activity. The enzymes of transamination between aspartic and ɑ-ketoglutaric acids and between alanine and ɑ-ketoglutaric have been found only in fractions migrating toward the cathode. Thus, by means of electrophoresis, it is possible to separate completely in the above structural elements of the kidney the enzyme catalyzing alanine synthesis from pyruvic acid, from the glutamic-pyruvic and glutamic-oxalacetic transaminases.