Exogenous proline-U-14C is readily metabolized to glutamate, ornithine, sugars, CO2, and organic acids, and is incorporated into protein by etiolated and green pumpkin cotyledons. As little translocation of proline from the cotyledons occur, it was proposed that in young tissue proline is converted to glutamate, ornithine or sugar which are then readily translocated from the cotyledons. In older tissue some glutamate carbon derived from proline is also used as an energy source and metabolized to CO2. As protein synthesis is occurring rapidly in these cotyledons, considerable proline is incorporated into new protein. After 10-hr, 15of the absorbed radioactivity still remained as free proline.
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