Recent advances in Levansucrase and Inulosucrase: evolution, characteristics, and application.

Levan and inulin are two types of fructan. Levan is composed of β -(2, 6) fructosyl linkage and inulin is composed of β -(2, 1) linkage. Both levan and inulin have been accepted and applied in the food, medicinal and chemical industries for their outstanding physicochemical properties in recent years. Microbial levansucrase and inulosucrase are key enzymes responsible for the synthesis of fructan from sucrose. In this review, levansucrase and inulosucrase are discussed together for the first time regarding the evolutionary relationships, bacteria origin, crystal structure, product-forming mechanism and commercial applications. Particularly, some insights into the product specificity about levansucrase and inulosucrase as well as the mechanism for product elongation for fructan are also discussed in the article.