D-tryptophan is the D-enantiomer of tryptophan. It has a role as a bacterial metabolite. It is a tryptophan and a D-alpha-amino acid. It is a conjugate base of a D-tryptophanium. It is a conjugate acid of a D-tryptophanate. It is an enantiomer of a L-tryptophan. It is a tautomer of a D-tryptophan zwitterion.