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 norsperimidine, 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⁺. 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 polyphenlalanine synthesis up to 2-fold with no significant increase in misincorporation of [14C] leucine. Other triamines having one or two methylene chains more than norspermidine were also effective in eliciting these effects. Futhermore, 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.