title: Mass spectrometric identification of a stable catalytic cysteinesulfinic acid residue in an enzymatically active chemically modified glucoamylase mutant.
abstract: Mass spectrometric identification of cysteinsulfinic acid resulting in restoration of activity of chemically modified Glu400 Cys catalytic-base glucoamylase (GA) mutants is described. This oxidation unexpectedly occurred during attempts to carboxyalkylate the Cys400 GA mutant using three different alkylation reagents. However, mass spectrometric peptide mapping did not show the presence of carboxyalkylation of the Cys400 residue but suggested an oxidation to cysteinsulfinic acid based on the observed mass increment. The presence of cysteinsulfinic acid was confirmed by employing matrix-assisted laser desorption/ionization mass spectrometry combined with post-source decay analysis. Furthermore, strong enhancement of metastable fragmentation was observed for peptides containing oxidized Cys in comparison with non-oxidized peptide.
authors.affiliation: Department of Molecular Biology, Odense University, Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: E
authors.initials: E
authors.lastname: Mirgorodskaya
authors.forename: H P
authors.initials: HP
authors.lastname: Fierobe
authors.forename: B
authors.initials: B
authors.lastname: Svensson
authors.forename: P
authors.initials: P
authors.lastname: Roepstorff
mesh_terms: D000595:Amino Acid Sequence; D002268:Carboxypeptidases; D043402:Cathepsin A; D003545:Cysteine / Q000031:analogs & derivatives* / Q000032:analysis; D005087:Glucan 1,4-alpha-Glucosidase / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D018377:Neurotransmitter Agents; D010446:Peptide Fragments / Q000737:chemistry*; D010843:Pichia / Q000201:enzymology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
chemical_list: D018377:Neurotransmitter Agents; D010446:Peptide Fragments; D005087:Glucan 1,4-alpha-Glucosidase; D002268:Carboxypeptidases; D043402:Cathepsin A; D003545:Cysteine; C013461:cysteine sulfinic acid