Experimental Evidence and In Silico Identification of Tryptophan Decarboxylase in Citrus Genus.

Plant tryptophan decarboxylase (TDC) converts tryptophan into tryptamine, precursor of indolealkylamine alkaloids. The recent finding of tryptamine metabolites in plants leads to hypothesize the existence of TDC activity in this genus. Here, we report for the first time that, in x seedlings, deuterium labeled tryptophan is decarboxylated into tryptamine, from which successively deuterated ,,-trimethyltryptamine is formed. These results give an evidence of the occurrence of the TDC activity and the successive methylation pathway of the tryptamine produced from the tryptophan decarboxylation. In addition, with the aim to identify the genetic basis for the presence of TDC, we carried out a sequence similarity search for TDC in the genomes using as a probe the TDC sequence reported for the plant . We analyzed the genomes of both and , available in public database, and identified putative protein sequences of aromatic l-amino acid decarboxylase. Similarly, 42 aromatic l-amino acid decarboxylase sequences from 23 plant species were extracted from public databases. Potential sequence signatures for functional TDC were then identified. With this research, we propose for the first time a putative protein sequence for TDC in the genus .