The Q-Trap mass spectrometer, a novel tool in the study of protein glycosylation.

The use of the recently introduced Q-Trap mass spectrometer in the study of protein glycosylation is described. The combined ion trap and triple quadrupole scan functions make it a powerful system in both oligosaccharide and glycopeptide analysis. Several oligosaccharides, both linear and branched, were analyzed to obtain information on sequence, linkage, and branching. Quadrupole like MS/MS spectra with ion trap sensitivity but without the typical ion trap low mass cut-off were obtained. To determine the origin of fragments and to reveal the existence of new ions, the MS(3) capabilities of the system proved to be useful. Glycopeptides were selectively detected in peptide mixtures using the triple quadrupole precursor ion scan function, either in off-line experiments or during LC/MS using information dependent acquisition (IDA).

Novel tools for the study of class I alpha-mannosidases: a chromogenic substrate and a substrate-analog inhibitor.

The use of chromogenic substrates for evaluation of class I alpha-mannosidase is described. 2('),4(')-Dinitrophenyl-alpha-D-mannopyranoside allows rapid and sensitive assays of enzymatic activities, e.g., of heterologously expressed alpha-1,2-mannosidase from Trichoderma reesei. Interaction constants of several ligands with alpha-mannosidases from class I and II could also be determined. Furthermore, novel types of inhibitors derived from D-lyxose are presented. Methyl-alpha-D-lyxopyranosyl-(1(')-->2)-alpha-D-mannopyranoside is a potent inhibitor of the alpha-1,2-mannosidase from T. reesei (K(i)=600 microM) and since it probably spans subsites -1/+1, this disaccharide could be valuable in crystallographic studies of class I alpha-mannosidases.