PMC

Chemical structures of the primary mammalian polyamines.

Chemical structure of curcumin, the principle active curcuminoid component of turmeric

The mammalian polyamine pathway. Polyamines are derived from the amino acid ornithine, which is decarboxylated by ornithine decarboxylase (ODC) to form the diamine putrescine. Putrescine undergoes the sequential addition of 2 aminopropyl groups to form spermidine followed by spermine. These reactions are catalyzed by the spermidine and spermine synthases (SRM and SMS, respectively), using decarboxylated S-adenosylmethionine as the aminopropyl donor. Catabolism of spermine back to spermidine can occur through direct oxidation via spermine oxidase (SMOX) or by acetylation at the N¹ position by spermidine/spermine N¹-acetyltransferase (SSAT), followed by oxidation by the acetylpolyamine oxidase (PAOX). This latter two-step mechanism also back-converts spermidine to putrescine via an N¹-acetylspermidine (N¹-AcSpd) intermediate. Alternatively, acetylated spermine and spermidine can be readily exported from the cell.