Effect of purification of galactooligosaccharides derived from lactulose with Saccharomyces cerevisiae on their capacity to bind immune cell receptor Dectin-2

Abstract

Lactulose-derived oligosaccharides (OsLu) are prebiotic galactooligosaccharides (GOS) beneficial for human health including immunomodulatory properties; however, the molecular mechanism is unclear. OsLu produced by enzymatic synthesis can be purified with Saccharomyces cerevisiae (OsLu-Sc). We show that this purification introduces yeast-derived proteins reactive to Dectin-2, an innate immune receptor for fungal polysaccharides. Using a cell-based bioassay, we tested the binding of OsLu and GOS samples to Dectin-2. While OsLu purified with active charcoal and commercial GOS failed to bind to Dectin-2, we found OsLu-Sc bound to this receptor. The carbohydrate-binding incompetent mutant of Dectin-2 failed to bind to OsLu-Sc. These data suggest that OsLu-Sc introduced carbohydrate ligands for Dectin-2. In accordance with this, proteomic analysis revealed OsLu-Sc contained S. cerevisiae-derived mannoproteins. Therefore, our data highlight the importance of the purification method for OsLu, which may positively affect the bioactivity of OsLu. Data are available via ProteomeXchange with identifier PXD010495.

Keywords: Dectin-2; Lactulose; Mannoproteins; Oligosaccharides; Prebiotics; Saccharomyces.