Structure of glycosylated Cu/Zn-superoxide dismutase from Kluyveromyces yeast NBIMCC 1984

The primary structure of Cu/Zn-superoxide dismutase from Kluyveromyces marxianus NBIMCC 1984 was elucidated by N-terminal sequence analysis of the intact protein and by determination of the amino acid sequences of tryptic peptides by MALDI–TOF–TOF tandem mass spectrometry. The molecular mass of one subunit of the homodimer SOD, containing 152 amino acid residues, was calculated to be 15858.3Da while a value of 17096.63Da was obtained by MALDI–TOF MS. This difference is explained by the presence of N-glycosylation of one linkage site, -Asn-Ile/Leu-Thr-, and a glycan chain with the structure Hex5 GlcNAc2. Glycosylation of K. marxianus superoxide dismutase is a post-translational modification. Recent developments in mass spectrometry have enabled detailed structural analyses of covalent modifications of proteins. Therefore, in this paper, we introduce a covalent modification of Cu/Zn-SOD from K. marxianus NBIMCC 1984, by analysis of the enzymatic liberated N-glycan from the enzyme using MALDI–TOF and tandem mass spectrometry on a Q-Trap mass spectrometer.