N-Glycosylation patterns in two α-L-arabinofuranosidases from Penicillium canescens belonging to the glycoside hydrolase families 51 and 54

Using MALDI-TOF mass spectrometry (MS) peptide fingerprinting procedure followed by the analysis of MS data with the GlycoMod tool from the ExPASy proteomic site, N-glycosylation of two GH51 and GH54 family alpha-L-arabinofuranosidases (Abf51A and Abf54A) from Penicillium canescens was studied. Variable N-linked glycans were identified at five out of eight potential N-glycosylation sites in the Abf51A and one out of three potential N-glycosylation sites in the Abf54A. The discriminated glycans represented high-mannose oligosaccharides (Man) x(GlcNAc) 2 with a number of Man residues up to 7 or the products of sequential enzymatic trimming of a high-mannose glycan with alpha-mannosidases and beta-N-acetylhexosaminidases. The Abf54A peptide, containing the Asn254 glycosylation site, and one peptide from the Abf51A, containing the Asn163 glycosylation site, were found to exist not only in glycosylated, but also in a native non-modified form. (C) 2013 Elsevier Ltd. All rights reserved.