N(8)-citryl-spermidine + spermidine + ATP => N(8),N'(8)-citryl-bis(spermidine) + AMP + diphosphate + H(+)
n(8)-citryl-spermidine + spermidine + atp => n(8),n'(8)-citryl-bis(spermidine) + amp + diphosphate + h(+)