SAM and polyamines

Just to emphasise that methylation is not the only trick up SAM's sleeve, it's also involved in the production of the polyamines. Spermidine and spermine are synthesised using the putrescine backbone derived from arginine:

arginine -(arginase)-> ornithine -(ornithine decarboxylase)-> putrescine

S-adenosyl methionine -(S-adenosyl methionine decarboxylase)-> decarboxylated SAM

putrescine + decarboxylated SAM -(spermidine synthetase)-> spermidine

spermidine + decarboxylated SAM -(spermine synthetase)-> spermine


Polyamines are important for balancing the negative charge of nucleic acids amongst other things and are therefore essential in all cells and especially in cells undergoing proliferation. For instance, in my preferred animal model, polyamines have been shown to be key factors controlling Leishmania major proliferation.