Abstract
When tissue suspensions containing mitochondria and microsomes prepared from rat spleen, bone marrow and transplanted Murphy lymphosarcoma were incubated with fructose diphosphate under aerobic conditions, an energy-dependent incorporation of amino acids took place. Whereas the extent of incorporation of C14-labeled glycine, alanine and glutamic acid was of the same order in such preparations of liver and spleen, C14-labeled leucine and lysine were more activity incorporated in the preparations from liver. When C14-lysine, but not the other amino acids tested, was incubated with spleen-cell sap, the isolated protein was radioactive. The labeling of this protein was only slightly affected by the presence of Ca++ or PO4[long dash]in the medium. When suspensions of lymphatic tissues were freed of mitochondria and incubated under anaerobic conditions with phosphoenolyruvate, C14 alanine and C14-leucine were incorporated. Active microsomes could be obtained from these tissues by either ultracentrifuging or aggregation with Mg++. When the microsomes prepared from spleen or liver were incubated with cell sap and phosphoenolpyruvate, alanine was incorporated to about the same extent in the 2 preparations whereas leucine was more actively incorporated in the preparation from liver. When liver-cell sap was replaced by spleen-cell sap the incorporation of C14-alanine into liver microsomes was enhanced whereas the incorporation of C14-leucine was only slightly affected. On the other hand, the replacement of spleen-cell sap by liver-cell sap reduced the incorporation of both amino acids into spleen microsomes. When the fraction of the spleen-cell sap precipitated at pH 5.2 replaced a similar fraction from liver, the incorporation of both amino acids into spleen and liver microsomes was reduced.