In Vitro Human Sialylation of Bovine Immunoglobulin G and Preparation of Fc Fragment from It

In the present study, a method for enzymatically digesting N-glycolylneuraminic acid (Neu5Gc) in bovine immunoglobulin G (bIgG) and then ligating the IgG with human N-acetylneuraminic acid (Neu5Ac) was developed to transform bIgG into human IgG (hIgG), and conditions for preparing a crystallizable fragment (Fc) from hIgG were explored. Results showed that hIgG was prepared by digesting Neu5Gc in bIgG (4 mg/mL) with 170 U/mL neuraminidase and subsequently transferring 8.4 galactose (Gal) residues and 42 Neu5Ac residues into the digested IgG with β-1,4-galactosyltransferase (B4GALT1) and α-2,6-sialyltransferase (ST6GAL1), respectively. Further, a highly pure Fc fragment from hIgG was prepared under the conditions: hIgG concentration 10 mg/mL, papain/hIgG ratio 0.05 (m/m), cysteine concentration 10.0 mmol/L, EDTA concentration 2.0 mmol/L, pH 7.0, and hydrolysis time 3 h. The yields of glycosylated hIgG and Fc fragment were 71.7% and 20.8%, respectively. The results of the present study can provide a scientific basis for the development and nutritional evaluation of bIgG-based products.