Spermidine is numbered so that atom N-1 is in the amino group of the aminopropyl part of the molecule. The enzyme from Escherichia coli is bifunctional and also catalyses the glutathionylspermidine synthase (EC 22.214.171.124) reaction, resulting in a net hydrolysis of ATP.
Bollinger, J.M., Kwon, D.S., Huisman, G.W., Kolter, R., Walsh, C.T. Glutathionylspermidine metabolism in E. coli. Purification, cloning, overproduction and characterization of a bifunctional glutathionylspermidine synthetase/amidase. J. Biol. Chem.270 (1995) 14031–14041. [PMID: 7775463]