Creation of thermostable l-tryptophan dehydrogenase by protein engineering and its application for l-tryptophan quantification

Abstract

l-Tryptophan dehydrogenase is a new NAD+-dependent amino acid dehydrogenase discovered in Nostoc punctiforme. The enzyme is involved in scytonemin biosynthesis and is highly selective toward l-tryptophan. By a growth-dependent molecular evolution technique, a thermostable mutant enzyme was selected successfully. l-Tryptophan concentration in human plasma was successfully determined using the thermostable mutant of l-tryptophan dehydrogenase.