Abstract
4-Fluoro- and 4-nitro-phenylalanines inhibited the phenylalanine incorporation in a cell-free system of Ehrlich mouse ascites tumor cells, and their inhibition occurred in two steps, i.e. amino acid activation and transfer of phenylalanine to microsomes in protein synthesis. In the over-all incorporation experiment of a cell-free system, there was seen an antagonism of incorporation between phenylalanine and 4-fluorophenylalanine. The phenylalanine analogs did not exert their inhibitions on the incorporation of a few tested amino acids other than phenylalanine. Furthermore, the fluoro and nitro analogs behaved differently on the phenylalanine accumulation into "amino acid pool"of intact cells, the former being stimulative and the latter a little inhibitory. Discussions were made on several problems encountered in the inhibition of protein synthesis by the analogs.
