1986 Volume 89 Issue 6 Pages 715-723
Since detailed analysis on the structure and property of mucin in human nasal secretion has not so far performed due to the difficulty of its solubilization, we aimed to investigate the solubilization and the carbohydrate composition of the mucin to clarify the function and the possible involvement by pathological conditions.
Nasal mucopurulent secretions obtained from patients of chronic sinusitis (17 cases, 30ml, dry weight 1650mg) were solubilized with 5mM EDTA-containing phosphate buffered saline (PBS, pH 7.4), and the insoluble materials which were hardly solubilized under the above condition, were solubilized with 8M urea in PBS. According to the two step solubilization procedures, almost all of the nasal secretions could be solubilized and the recoveries of dry weight, protein, hexose and sialic acid were 92.9%, 71.5%, 96.4% and 92.9%, respectively. The soluble fraction with EDTA-PBS and the fraction solubilized with urea-PBS (insoluble fraction) were fractionated by Sepharose CL-4B column chromatography and the mucin fractions in the void volume, which contained glycoprotein with the molecular weight of more than 105 daltons, were collected. Both mucins retained on a DEAE Sephadex A-25 column, indicating that the majority of the mucins are negatively charged, and their purity and molecular weights were confirmed by SDS-Polyacrylamide Gel Electrophoresis.
In addition, carbohydrate compositions of both soluble and insoluble mucins were determined by gas-liquid chromatography. Molar ratio of carbohydrates in the soluble mucin was Fuc: Man: Gal:GaINAc:G1cNAc:NeuAc=2.31: 0.13:4.36:0.99:1.81:1, and that in the insoluble mucin was Fuc:Man:Gal:Ga1NAc:G1cNAc:NeuAc=1.93:0.33:5.68:2.63:5.44:1. The difference between the two mucins with different solubilities was suggested to be mainly due to the aminosugar, which mediate the formation for intra-and inter-molecular linkages to give the viscous nature of the mucin.
