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

N¹-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.