Biosynthesis

Dimethyltryptamine is an indole alkaloid derived from the shikimate pathway. Its biosynthesis is relatively simple and summarized in the adjacent picture. In plants, the parent amino acid L-tryptophan is produced endogenously where in animals L-tryptophan is an essential amino acid coming from diet. No matter the source of L-tryptophan, the biosynthesis begins with its decarboxylation by an aromatic amino acid decarboxylase (AADC) enzyme (step 1). 

The resulting decarboxylated tryptophan analog is tryptamine. 

Tryptamine then undergoes a transmethylation (step 2): the enzyme indolethylamine-N-methyltransferase (INMT) catalyzes the transfer of a methyl group from cofactor S-adenosyl-methionine (SAM), via nucleophilic attack, to tryptamine. This reaction transforms SAM into S-adenosylhomocysteine (SAH), and gives the intermediate product N-methyltryptamine (NMT).

NMT is in turn transmethylated by the same process (step 3) to form the end product N,N-dimethyltryptamine. 

Tryptamine transmethylation is regulated by two products of the reaction: SAH, and DMT were shown ex vivo to be among the most potent inhibitors of rabbit INMT activity.

This transmethylation mechanism has been repeatedly and consistently proven by radiolabeling of SAM methyl group with carbon-14 (14C-CH3)SAM.