Carboxynorspermidine decarboxylase (, carboxyspermidine decarboxylase, CANSDC, VC1623 (gene)) is an enzyme with systematic name carboxynorspermidine carboxy-lyase (bis(3-aminopropyl)amine-forming). This enzyme catalyses two related decarboxylation reactions.
The enzyme contains pyridoxal 5'-phosphate. It acts on biosynthetic intermediates which are produced by the enzyme carboxynorspermidine synthase and together these are the main way that bacteria which form the gut microbiota in humans make spermidine and norspermidine.