Enzymic decarboxylation of s-adenosyl-l-methionine in rat liver: possible interaction of putrescine with the prosthetic group.

S-Adenosyl-L-methionine decarboxylase (EC 4.1.1.50) has been purified more than 1000-fold from rat liver. The molecular weight of the decarboxylase was calculated to be 68 000. No evidence was obtained indicating that pyridoxal phosphate acts as the prosthetic group of the enzyme. On the other hand, the decarboxylase apparently contains some carbonyl group(s) participating in the catalysis as supported by the inhibition of S-adenosyl-L-methionine decarboxylation in the presence of NaBH-4, phenylhydrazine or NaCN. Putrescine, the specific activator of mammalian S-adenosyl-L-methionine decarboxylase, might interact, directly or indirectly, with the carbonyl group(s) of the enzyme as suggested by the protection of the decarboxylase activity against borohydride reduction by the diamine.