Structural and Functional Features of Ketoso-3-Epimerases and Their Use in Production of D-Allulose

Abstract

Rare sugars attract more and more attention as safe, low-calorie sweeteners and functional compounds in the food, pharmaceutical and medical industries. The potential of the rare sugar D-allulose has been proven in a large number of theoretical and applied works but the high cost of its production is a limitation factor for its large-scall production. Epimerization reactions of available sugars leading to the production of D-allulose are catalyzed by enzymes consisting the epimerase group, namely, ketose-3-epimerases. The key goals of ongoing studies on the ketose-3-epimerase family enzymes are focused on the exact mechanisms of their work, improvement of the enzymatic activity and stability in order to achieve high efficiency in the production of D‑allulose. The present review summarizes the latest innovative developments in use of ketose-3-epimerases, as well as optimization of the enzymatic processes of D-allulose production. The structural features of the main enzymes used in the production of this rare sugar, variants of molecular modifications of biocatalysts and prospects for the practical use of the enzyme pathways discussed in this work are considered.