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

Abstract

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 α-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 α-mannosidases and β-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.

Keywords: Glycoproteins; High-mannose glycans; MALDI-TOF mass spectrometry; N-Glycosylation; Penicillium canescens; α-l-Arabinofuranosidase.