Influence of glycosylation on the drug binding of human serum albumin.

The influence of glycosylation on the drug binding of human serum albumin (HSA) was studied using HSA containing different amounts and degrees of glycosylated HSA. The drugs used were furosemide, naproxen, procaine, phenylbutazone, salicylic acid, sulphamethoxazole, tolbutamide and warfarin. The drug-HSA parameters (lognK) were measured by the ultrafiltration method, frontal analysis and a modified Hummel-Dreyer method. The modified Hummel-Dreyer method was the simplest method with high precision and required the smallest amounts of proteins. The lognK values were well correlated with the octanol-water partition coefficients; the correlation coefficients were over 0.95. The results suggested that hydrophobic interaction is the predominant force for the drug binding. The early stage of glycosylation of HSA did not significantly affect the drug-binding capacity. Generally, the binding affinity of HSA decreased, perhaps due to a conformational change or steric hindrance (except naproxen) when further glycosylation occurred.