Autocatalytic Mechanism in the Anaerobic Reduction of Metmyoglobin by Sulfide Species.
Inorg Chem
; 62(29): 11304-11317, 2023 Jul 24.
Article
em En
| MEDLINE
| ID: mdl-37439562
ABSTRACT
The mechanism of the metal centered reduction of metmyoglobin (MbFeIII) by sulfide species (H2S/HS-) under an argon atmosphere has been studied by a combination of spectroscopic, kinetic, and computational methods. Asymmetric S-shaped time-traces for the formation of MbFeII at varying ratios of excess sulfide were observed at pH 5.3 < pH < 8.0 and 25 °C, suggesting an autocatalytic reaction mechanism. An increased rate at more alkaline pHs points to HS- as relevant reactive species for the reduction. The formation of the sulfanyl radical (HSâ¢) in the slow initial phase was assessed using the spin-trap phenyl N-tert-butyl nitrone. This radical initiates the formation of S-S reactive species as disulfanuidyl/ disulfanudi-idyl radical anions and disulfide (HSSHâ¢-/HSSâ¢2- and HSS-, respectively). The autocatalysis has been ascribed to HSS-, formed after HSSHâ¢-/HSSâ¢2- disproportionation, which behaves as a fast reductant toward the intermediate complex MbFeIII(HS-). We propose a reaction mechanism for the sulfide-mediated reduction of metmyoglobin where only ferric heme iron initiates the oxidation of sulfide species. Beside the chemical interest, this insight into the MbFeIII/sulfide reaction under an argon atmosphere is relevant for the interpretation of biochemical aspects of ectopic myoglobins found on hypoxic tissues toward reactive sulfur species.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Sulfeto de Hidrogênio
/
Metamioglobina
Idioma:
En
Ano de publicação:
2023
Tipo de documento:
Article