β-Galactosidase treatment is a common first-stage modification of the three major subtypes of Gc protein to GcMAF.

Background: The 1f1f subtype of the group- specific component (Gc) protein is converted into Gc protein- derived macrophage-activating factor (GcMAF) by enzymatic processing with β-galactosidase and sialidase. We previously demonstrated that preGc 1f1f MAF, a full Gc 1f1f protein otherwise lacking a galactosyl moiety, can be converted to GcMAF by treatment with mouse peritoneal fluid. Here, we investigated the effects of the β-galactosidase-treated 1s1s and 22 subtypes of Gc protein (preGc 1s1s MAF and preGc 22 MAF) on the phagocytic activation of mouse peritoneal macrophages. Results: We demonstrated the presence of Gal-GalNAc disaccharide sugar structures in the Gc 1s1s protein by western blotting using peanut agglutinin and Helix pomatia agglutinin lectin. We also found that preGc 1s1s MAF and preGc 22 MAF significantly enhanced the phagocytic activity of mouse peritoneal macrophages in the presence and absence of mouse peritoneal fluid. Conclusion: We demonstrate that preGc 1s1s MAF and preGc 22 MAF proteins can be used as effective macrophage activators. The group-specific component (Gc) protein, a vitamin D- binding protein (DBP), Gc globulin, is a 53-kDa human