title: A new method for the detection and characterization of alpha-lipoic acid mixed disulphides.
abstract: Alpha-lipoic acid (LA) acts as a direct regulator of intracellular redox status through the formation of mixed disulphides. However, as this is reversible, the evidence for the mixed disulphides has not been obtained. This study established a method for the detection and characterization of mixed disulphides by mass spectrometry (MS) and was the first to provide direct evidence for their formation. When cysteine methyl ester was incubated with LA in the presence of iodeacetamide (IAA), a mixed disulphide with mono carbamidomethylation was observed. MS/MS analysis indicated that the LA forms a mixed disulphide with the cysteinyl sulphydryls, while the other sulphydryl group is the carbamidomethylated. The same results were obtained from the incubation of sulfphydryl peptides such as glutathione with LA in the presence of IAA. These results may provide further biological evidence that LA is a potential modifier of intracellular sulphydryls through mixed disulfide formation.
authors.affiliation: Department of Food and Nutritional Sciences, and Global COE Program, University of Shizuoka, 52-1 Yada, Suruga-ku Shizuoka 422-8526, Japan. ishii_t@u-shizuoka-ken.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ishii
authors.forename: Miyuki
authors.initials: M
authors.lastname: Wakabayashi
authors.forename: Taiki
authors.initials: T
authors.lastname: Mori
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakayama
mesh_terms: D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000031:analogs & derivatives / Q000737:chemistry; D004220:Disulfides / Q000032:analysis* / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry; D019803:Glutathione Disulfide / Q000737:chemistry; D007460:Iodoacetamide / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013438:Sulfhydryl Compounds / Q000737:chemistry; D053719:Tandem Mass Spectrometry; D008063:Thioctic Acid / Q000031:analogs & derivatives / Q000032:analysis* / Q000737:chemistry
chemical_list: D004220:Disulfides; D010446:Peptide Fragments; D013438:Sulfhydryl Compounds; D008063:Thioctic Acid; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D005978:Glutathione; D003545:Cysteine; C017507:mecysteine; D019803:Glutathione Disulfide; D007460:Iodoacetamide