Dehydroascorbic acid S-Thiolation of peptides and proteins: Role of homocysteine and glutathione.
Free Radic Biol Med
; 141: 233-243, 2019 09.
Article
en En
| MEDLINE
| ID: mdl-31228548
ABSTRACT
Ascorbic acid (vitamin C) plays a significant role in the prevention of oxidative stress. In this process, ascorbate is oxidized to dehydroascorbate (DHA). We have investigated the impact of DHA on peptide/protein intramolecular disulfide formation as well as S-glutathionylation and S-homocysteinylation. S-glutathionylation of peptides/proteins is a reversible, potential regulatory mechanism in oxidative stress. Although the exact role of protein S-homocysteinylation is unknown, it has been proposed to be of importance in pathobiological processes such as onset of cardiovascular disease. Using an in vitro model system, we demonstrate that DHA causes disulfide bond formation within the active site of recombinant human glutaredoxin (Grx-1). DHA also facilities the formation of S-glutathionylation and S-homocysteinylation of a model peptide (AcFHACAAK) as well as Grx-1. We discuss the possible mechanisms of peptide/protein S-thiolation, which can occur either via thiol exchange or a thiohemiketal intermediate. A thiohemiketal DHA-peptide adduct was detected by mass spectrometry and its location on the peptide/protein cysteinyl thiol group was unambiguously confirmed by tandem mass spectrometry. This demonstrates that peptide/protein S-thiolation mediated by DHA is not limited to thiol exchange reactions but also takes place directly via the formation of a thiohemiketal peptide intermediate. Finally, we investigated a potential reducing role of glutathione (GSH) in the presence of S-homocysteinylated peptide/protein adducts. S-homocysteinylated AcFHACAAK, human hemoglobin α-chain and Grx-1 were incubated with GSH. Both peptide and proteins were reduced, and homocysteine replaced with GS-adducts by thiol exchange, as a function of time.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Péptidos
/
Compuestos de Sulfhidrilo
/
Ácido Deshidroascórbico
/
Glutarredoxinas
/
Glutatión
/
Homocisteína
Límite:
Humans
Idioma:
En
Revista:
Free Radic Biol Med
Asunto de la revista:
BIOQUIMICA
/
MEDICINA
Año:
2019
Tipo del documento:
Article
País de afiliación:
Canadá