Further studies on the peptido-galactomannan from the yeast form of Cladosporium werneckii - Identification of O-acetyl substituents and isolation of the peptide components following β-elimination - Lee, W.-L.; Lloyd, K.O. (Elsevier)
The pathogenic yeast Cladosporium werneckii produces a surface peptido-phosphogalactomannan (PPGM) with a peptide backbone rich in serine and threonine to which three types of carbohydrate chains are linked. These chains are: Type a, glactomannan units linked through phosphodiester bonds to produce long chains of molecular weight about 50,000; type b more numerous short mannosyl oligosaccharide units, and type c, more infrequent, long galactomannan chains. The first two are linked to the peptide through alkali-labile bonds to serine and threonine of the peptide whereas type c chains are linked through alkali-stable bonds (Lloyd, K. O. (1972) Biochemistry, 11, 3884-3890). The PPGM sample can be separated into three or four major components by diethylaminoethyl (DEAE-) Sephadex chromatography. By means of sequential degradations with alkali and acid, the structural basis for this heterogeneity has been demonstrated. It is due to the presence of different proportions of the three types of chains in the various fractions. The presence of O-acetyl groups, mainly on the a chains, was demonstrated in PPGM by chemical analysis and by proton and ^1^3C nuclear magnetic resonance spectroscopy. Purified a chains were isolated from PPGM following Pronase digestion. By taking advantage of the alkali lability of the carbohydrate-protein linkages it has been possible to cleave the peptide moiety away from the carbohydrate. By sequential chromatography on Bio-Gel P-100, Dowex 1 and Bio-Gel P-100, five modified peptide fractions were isolated. The molecular weights of these fractions varied from 9,500 to 18,500 as judged by polyacrylamide-gel electrophoresis. Unlike the original peptide, the modified peptides contained low amounts of serine and threonine. The predominant amino acids were alanine, glycine, aspartic acid and glutamic acid which together make up between 51 and 55% of the peptides. The high content of the last two amino acids accounts for the acidic nature of the peptides. It appears that each fraction consists of a slightly heterogeneous population of peptides very similar in amino acid composition. It is not clear whether the compositional and size heterogeneity exists in the original peptide or whether it arose during the isolation procedure.
http://dx.doi.org/10.1016/0003-9861(75)90071-5
Keywords: W; V; U