title: Derivatization of gamma-glutamyl semialdehyde residues in oxidized proteins by fluoresceinamine.
abstract: Oxidative modification of proteins is implicated in a number of physiologic and pathologic processes. Metal-catalyzed oxidative modification usually causes inactivation of enzymes and the appearance of carbonyl groups in amino acid side chains of the protein. We describe use of fluoresceinamine to label certain of those carbonyl groups. Fluoresceinamine reacted with those carbonyl groups to form a Schiff base which was reduced by cyanoborohydride to yield a stable chromophore on the oxidized residue. The high molar absorbtivity of the fluorescein moiety conferred high sensitivity upon the method. Labeled peptides were readily identified after tryptic digestion of oxidized glutamine synthetase. Further, acid hydrolysis of labeled glutamine synthetase allowed isolation of the derivatized, oxidized residue. The oxidized amino acid was identified as gamma-glutamyl semialdehyde. During metal-catalyzed oxidation, the inactivation of glutamine synthetase paralleled the appearance of gamma-glutamyl semialdehyde.
authors.affiliation: Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892.
authors.forename: I
authors.initials: I
authors.lastname: Climent
authors.forename: L
authors.initials: L
authors.lastname: Tsai
authors.forename: R L
authors.initials: RL
authors.lastname: Levine
mesh_terms: D000447:Aldehydes / Q000032:analysis; D001894:Borohydrides; D004789:Enzyme Activation; D005452:Fluoresceins; D005974:Glutamate-Ammonia Ligase / Q000032:analysis; D005971:Glutamates / Q000032:analysis*; D007659:Ketones / Q000032:analysis; D010084:Oxidation-Reduction; D010449:Peptide Mapping; D011506:Proteins / Q000032:analysis
chemical_list: D000447:Aldehydes; D001894:Borohydrides; D005452:Fluoresceins; D005971:Glutamates; D007659:Ketones; D011506:Proteins; C021199:glutamic acid gamma-semialdehyde; C032376:fluoresceinamine isomer II; C009282:sodium cyanoborohydride; D005974:Glutamate-Ammonia Ligase