An enzyme that catalyzes the decarboxylation of S-adenosyl-L-methionine to yield 5'-deoxy-(5'-),3-aminopropyl-(1), methylsulfonium salt. It is one of the enzymes responsible for the synthesis of spermidine from putrescine. EC 4.1.1.50.

Synonyms: Adenosylmethionine Decarboxylase, EC 4.1.1.50, Decarboxylase, S-Adenosylmethionine, S Adenosylmethionine Decarboxylase, S-Adenosylmethionine Decarboxylase, S-Adenosyl-L-methionine carboxy-lyase, Decarboxylase, Adenosylmethionine