Treatment of murine leukemic (L5178Y) lymphoblasts in vitro with phenylalanine ammonia-lyase resulted in a decrease in protein synthesis, followed by decreases in RNA and DNA synthesis, inhibition of cell division, and a loss of cell viability. Compared with enzyme treatment, phenylalanine deprivation resulted in similar decreases in cell viability. These results confirm earlier studies and further support the concept that phenylalanine ammonia-lyase exerts its inhibitory effect by depriving rapidly dividing cells of the essential amino acid phenylalanine.

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This investigation was supported by USPHS Research Grant CA-11732 from the National Cancer Institute.

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