Tryptophanase-catalysed degradation of D-tryptophan in highly concentrated diammonium hydrogen phosphate solution

Tryptophanase is and is perfectly inert to D-tryptophan under ordinary conditions. However, activity that can degrade D-tryptophan into indole is observed when tryptophanase is in highly concentrated diammoniumhydrogen phosphate solution. The reaction has been so far unknown in tryptophanase metabolic pathways. Here we report the characteristic of the reaction. We also discuss its significance in relation to selection of an amino acid optical isomer from a racemic mixture.