Characterization of the carbohydrate moiety in a partly purified allergen preparation from the mould Cladosporium herbarum and its possible importance for allergenic activity as tested by RAST-inhibition.

The monosaccharide composition of a partly purified Cladosporium herbarum allergen preparation was found to be mannose, galactose and glucose in the ratio 1:1:0.8. The carbohydrate part of the preparation was quantified to 55% of the dry weight material by means of methanolysis and gas liquid chromatography (GLC) of trimethylsilylated methyl glycosides. The protein content was found to be 25%, determined by the Lowry method. Methylation analysis and periodate oxidation indicated that the main part of the carbohydrate moiety consists of galactomannans and glucans. It is suggested that the galactomannan is a highly branched polymer with mannopyranose units, 1,2- and 1,6-linked in the main chain, having shorter chains of 1,6-linked galactofuranosyl units linked through position 3 of the 1,6-linked mannopyranose units. The glucan part is probably a mixture of several polymers consisting of 1,3-linked and 1,4-linked glucans. The radioallergosorbent test (RAST) inhibition showed a lower IgE binding capacity for periodate-treated mould preparations, in which sugars containing vicinal diols had been oxidized, suggesting that the carbohydrate moiety may be of importance in IgE binding reaction of allergens. Periodate oxidation did not seem to alter the amino acid composition of the protein.