Purification and partial characterization of the allergen Ag-54 from Cladosporium herbarum

One important allergen, Ag-54, was extracted from Cladosporium herbarum and purified by a combination of diafiltration, gel filtrations and isoelectric focusing. The allergen, when examined by gel electrophoresis and high-performance liquid chromatography, was found to be essentially homogeneous with a molecular weight of about 20,000 daltons. Ag-54 is of glycoprotein nature. It contained 19.5% protein, calculated from its amino acid composition and 80.2% carbohydrate, quantified by methanolysis, trimethylsilyl derivatization and gas-liquid chromatography. The carbohydrate moiety was composed only of mannose, galactose and glucose in the ratio 1.0:0.6:1.3. Frequently occurring amino sugars like glucosamine and galactosamine could not be detected. Mass spectrometry of trimethylsilyl-derivatized methylglycosides demonstrated that sialic acid was not present.