Xylose isomerase from Piromyces: Characterization and engineering for improving S. cerevisiae-based lignocellulosic bioethanol production

Abstract

Xylose isomerases are tetrameric metalloenzymes that catalyze aldoseketose interconversion. Their activity is widely used in industrial biocatalysis, especially for the preparation of high-fructose syrups from glucose-containing starch hydrolysates. The activity with xylose is industrially relevant because it converts xylose that cannot be fermented by yeast to xylulose, which is accepted as a substrate for alcoholic fermentation. Several crystal structures of xylose isomerases have been solved and the catalytic mechanism has been investigated, opening the way to engineering more efficient variants of these enzymes. The properties of xylose isomerases and the potential of protein engineering to improve xylose metabolism by yeast are discussed here.