Structural Characterization of N‐Linked Oligosaccharides from Cellobiohydrolase I Secreted by the Filamentous Fungus Trichoderma Reesei RUTC 30

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Abstract
We have characterized the primary structures of the predominant N-linked oligosaccharides on cellobiohydrolase I from the filamentous fungus Trichoderma reesei RUTC30. Different enzymatic and chro-matographic techniques were used to analyze six oligosaccharides. The combined data showed that the fungal carbohydrates have a core structure that is identical to the mammalian N-linked core. In the bulk of the N-glycans, the α-1,3 arm is extended with two mannoses and a glucose, suggesting incomplete processing of the oligosaccharides in the endoplasmic reticulum. The α-1,6 arm shows a remarkable heterogeneity: in addition to α-1,2-Man and α-1,6-Man, the presence of a terminal mannose a-1,6-phos-phodiester was observed. This latter substituent has not been characterized before on mannosidase-processed N-glycan and its function and synthesis pathway are entirely unknown. The predominant N-glycans on cellobiohydrolase I can be represented as follows: GlcMan8GIcNAc2, GlcMan7GlcNAc2, ManGlcNAc2, ManPGlcMan7GlcNAc2, GlcMan5GlcNAc2, and Man5GlcNAc2.