Hordeum vulgare CYP76M57 catalyzes C shortening of tryptophan side chain by C-N bond rearrangement in gramine biosynthesis.

The indole alkaloid gramine, 3-(dimethylaminomethyl)indole, is a defensive specialized metabolite found in some barley cultivars. In its biosynthetic process, the tryptophan (Trp) side chain is shortened by two carbon atoms to produce 3-(aminomethyl)indole (AMI), which is then methylated by N-methyltransferase (HvNMT) to produce gramine. Although side chain shortening is one of the crucial scaffold formation steps of alkaloids originating from aromatic amino acids, the gene and enzyme involved in the Trp-AMI conversion reactions are unknown.