抄録
The improved sensitivity and soft ionization characteristic of ESI-MS/MS and MALDI-TOF-MS were applied to the identification of characteristic fragment ions from C-terminal GPI-anchored peptides of bovine liver 5′-nucleotidase and other several GPI-anchored proteins. In the CID spectrum of ESI-MS/MS, characteristic fragment ions such as m/z 162 (glucosamine) and m/z 286 (mannose-phosphate-ethanolamine) were effectively identified. In matrix-assisted laser desorption/ionization (MALDI)-TOF-MS analysis, heterogeneous peaks of GPI-anchored peptides caused by sugar side chains were detected as single charged ions in positive mode analysis. In PSD analysis most of the expected product ions succeeding from the precursor GPI-anchored peptide were fully obtained. Thus ESI-MS/MS and PSD of MALDI-TOF-MS proved to be fairly effective in analyzing small amount of GPI-anchored structure less than 10 pmol. By LC-ESI-MS analysis, C-terminal peptides bearing the products of GPI were effectively detected by combination with in-source decay and multi-functional scanning for the several characteristic fragment ions from GPI-anchor structure. Existence of microheterogeneity was observed in the C-terminal GPI-anchored peptides from the 42 kDa and 40 kDa protein of bovine erythrocytes. By LC-ESI-MS, C-terminal GPI-anchor structure can be easily identified from the target protein even if its amino acid sequence data are not available.
