GLYCOSYLATED CU/ZN-SUPEROXIDE DISMUTASE FROM KLUYVEROMYCES YEAST, DETERMINED BY MASS SPECTROMETRY

The primary structure of Cu/Zn SOD from Kluyveromyces marxianus NBIMCC 1984 (Cu/Zn-KmSOD) was elucidated by N-terminal sequencing of the intact protein and by determination of the amino acid sequences of the tryptic peptides through MALDI-TOF-TOF. The molecular mass of the SOD homodimer subunit, containing 152 amino acid residues, was calculated to be 15858,3 Da while by MALDI-TOF 17096,63 Da were determined. Only one typtophan residue at position 33 and one linkage site -Asn-Ile/Leu-Thr-were identified in the polypeptide chain of Cu/Zn-KmSOD. The full oligosaccharide structure of the naturally glycosylated superoxide dismutase was determined by mass spectrometry. Enzymatialyc liberated N-glycan from the enzyme was analysed using MALDI-TOF and tandem mass spectrometry on a Q-Trap mass spectrometer. One methylated hexose and an external fucose, linked to the hexoses were identified in the glycan.