Bacterial carboxyspermidine route to spermidine

A reusable bacterial route in which carboxyspermidine dehydrogenase condenses putrescine with aspartate semialdehyde using NADPH to form carboxyspermidine, followed by decarboxylation of carboxyspermidine to spermidine. Diamine and aspartate-semialdehyde supply are pathway inputs rather than parts of this two-reaction module.

The reusable boundary is species-neutral, while this CONCRETE review uses exact Pseudomonas putida KT2440 UniProt exemplars on both leaves. PP_2928 is currently named saccharopine dehydrogenase in UniProt, but its PTHR43796 family assignment, domain architecture, adjacency to nspC, and the species-aware sequence analysis strongly support CASDH. The exact GO label for GO:0102143 is "carboxynorspermidine dehydrogenase activity"; the NCBIFAM:NF043000 exact-match mapping to this term covers EC 1.5.1.43, and use of putrescine yields carboxyspermidine, hence CASDH in this route. Putrescine and aspartate-semialdehyde production are substrate supply outside the core.