Identification of N1‐acetylnorspermidine in Vibrio parahaemolyticus and an enzyme activity responsible for its formation

N 1‐Acetylnorspermidine [CH3CONH(CH2)3NH(CH2)3NH3] was identified in Vibrio parahaemolyticus, which contains norspermidine as a major polyamine. This is the first example for the natural occurence of monoacetylated unusual polyamine. The N1‐acetylnorspermidine content was the highest 4 h after inoculation. Incubation of norspermidine and acetyl CoA with a cell extract from V. parahaemolyticus produced N1‐acetylnorspermidine. A remarkable increase in specific activity of the acetyltransferase was observed at the exponential phase of growth. Spermidine also served as a substrate for the enzyme, with the formation of two isomers of the acetylspermidines (N1‐acetylspermidine was predominant), but the reaction rate was less than 50% of that with norspermidine. These results suggest that norspermidine in V. parahaemolyticus may be associated with the cell growth and its role may be controlled through acetylation, as reported for spermidine in Escherichia coli.