Enzymic degradation of yeast cell-wall mannans and Galactomannans to polymeric fragments containing α-(1→6)-linked D-mannopyranose residues

Abstract

The cell-wall D-mannans of Candida parapsilosis, Endomycopsis fibuliger, Saccharomyces rouxii, Torulopsis apicola (Hajsig strain), and Torulopsis bombi were degraded with an exo α- D-mannosidase from Arthrobacter GJM-1 to their α-(1→6)-linked D-mannopyranose main-chains, as demonstrated by p.m.r. spectroscopy. D-galacto- D-mannans from Candida lipolytica, Torulopsis gropengiesseri, Torulopsis lactis-condensi, Torulopsis magnoliae, and Trichosporon fermentans could be degraded to polysaccharides containing mainly 6- O-linked α- D-mannopyranosyl residues following preferential removal of their enzyme-resistant, D-galactopyranosyl non-reducing end-units with acid. The D-mannans of Saccharomyces lodderi, Citeromyces matritensis, and Pichia pastoris could also be enzymically degraded to polysaccharides containing predominantly α-(1→6)-linked D-mannopyranosyl residues after hydrolysis of most of the β- D-linked residues in their side chains with acid. The exo α- D-mannosidase, as would be expected, produced β- D-mannose on splitting of an α-(1→2)-linked D-mannopyranose tetramer. It is, however, very selective in its action since it did not cleave α- D-Man p-(1→2)-β- D-Man p-(1→2)-β- D-Man p-(1→2)-β- D-Man p-(1→2)- D-Man. Apparently a D-mannopyranose non-reducing end-unit and two consecutive α- D-mannopyranose residues are required by the enzyme for cleavage of a substrate to take place.