glyXtoolMS: An Open-Source Pipeline for Semiautomated Analysis of Glycopeptide Mass Spectrometry Data

For glycoproteomic analyses several web tools and standalone software packages have been developed over the recent years. These tools support or replace the time-consuming, cumbersome, and error-prone manual spectra analysis and glycopeptide identification. However, existing software tools are usually tailored to one fragmentation technique and only present the final analysis results. This makes manual inspection and correction of intermediate results difficult or even impossible. We solved this problem by dividing the analysis tasks into modular tools with defined functions, which are executed within a software pipeline with a graphical editor. This gives users a maximum of flexibility and control over the progress of analyses. Here, we present the open-source Python software suite glyXtool(MS), developed for the semiautomated analysis of N- and O-glycopeptide fragmentation data. glyXtool(MS) is built around the pipeline engine of OpenMS (TOPPAS) and provides a glycopeptide analysis toolbox for the analysis, interpretation, and visualization of glycopeptide spectra. The toolbox encompasses (a) filtering of fragment spectra using a scoring scheme for oxonium ions, (b) in silico digest of protein sequences to collect glycopeptide candidates, (c) precursor matching to possible glycan compositions and peptide sequences, and finally, (d) an annotation tool for glycopeptide fragment ions. The resulting analysis file can be visualized by the glyXtool(MS)Evaluator, enabling further manual analysis, including inspection, verification, and various other options. Using higher-energy collisional dissociation data from human immunoglobulin gamma (IgG) and human fibrinogen tryptic digests, we show that glyXtool(MS) enables a fast, flexible, and transparent analysis of N- and O-glycopeptide samples, providing the user a versatile tool even for explorative data analysis. glyXtoolT(MS) is freely available online on https://github.com/glyXera/glyXtoolMS licensed under the GPL-3.0 open-source license. The test data are available via ProteomeXchange with identifier PXD009716.