Effect of Norspermidine and Its Related Triamines on the Cell-Free Polyphenylalanine Synthesizing System from Vibrio parahaemolyticus

The effect of norspermidine and its structurally related triamines on the cell-free polyphenylalanine synthesizing system from Vibrio parahaemolyticus was examined in connection with the requirement of the system for monovalent cation. In the absence of norspermidine, the maximal incorporation of [¹⁴C] phenylalanine into hot trichloroacetic acid insoluble material was observed under ionic conditions of 12 mM Mg²⁺ and 50 mM NH4. 4+. K⁺ could partially substitute for NH4, but Na⁺ could not. The addition of norspermidine to the polyphenylalanine synthetic reaction mixture not only lowered the optimal Mg²⁺ concentration, but it also stimulated. the polyphenylalanine synthesis up to 2-fold with no significant increase in misin of [¹⁴C] leucine. Other triamines having one or two methylene chains more than norspermidine were also effective in eliciting these effects. Furthermore, Na⁺ could not support the polyphenylalanine synthesis even in the presence of norspermidine and, on the contrary, inhibited the polyphenylalanine synthesis induced by NH4+ regardless of whether norspermidine was present or not. These findings are discussed in comparison with the properties of other bacterial cell-free systems.