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Mass spectrometric identification of a stable catalytic cysteinesulfinic acid residue in an enzymatically active chemically modified glucoamylase mutant
Author(s) -
Mirgorodskaya Ekaterina,
Fierobe HenriPierre,
Svensson Birte,
Roepstorff Peter
Publication year - 1999
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199909)34:9<952::aid-jms856>3.0.co;2-y
Subject(s) - chemistry , mass spectrometry , fragmentation (computing) , desorption , chromatography , peptide , catalysis , residue (chemistry) , matrix assisted laser desorption/ionization , protein mass spectrometry , reagent , organic chemistry , tandem mass spectrometry , biochemistry , adsorption , computer science , operating system
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. Copyright © 1999 John Wiley & Sons, Ltd.