Figure 1. Overview of bacterial HSS-related polyamines and bacterial HSS-catalyzed reactions.

(a) Two-dimensional structures of diamines (DAP, PUT, CAD) and agmatine (AGM). (b) Two-dimensional structures of triamines. (c) Known net reactions of the bacterial HSS⁹: Reaction 1: HSP formation from 2× PUT; reaction 2: general triamine formation from PUT and a second diamine (with n = [1 to 5]); reaction 3: bacterial HSS does not produce sym-norspermidine from 2× DAP; reaction 4: HSP, DAP, and PUT formation from SPD; reaction 5: HSP, DAP, and PUT formation from SPD and PUT; reaction 6: (4-aminobutyl)(5-aminopentyl)amine, HSP, DAP, and PUT formation from SPD and CAD.