Reduction of Ferrylmyoglobin by Hydrogen Sulfide. Kinetics in Relation to Meat Greening

Autor(es)

Libardi, Silvia H. ^[1] ; Pindstrup, Helene ^[2] ; Cardoso, Daniel R. ^[1] ; Skibsted, Leif H. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil

^[2] Univ Copenhagen, Dept Food Sci, DK-1958 Frederiksberg C - Denmark

• Tipo de documento: Artigo Científico
• Fonte: Journal of Agricultural and Food Chemistry; v. 61, n. 11, p. 2883-2888, MAR 20 2013.
• Citações Web of Science: 14

Resumo

The hypervalent meat pigment ferrylmyoglobin, MbFe(IV)=O, characteristic for oxidatively stressed meat and known to initiate protein cross-linking, was found to be reduced by hydrogen sulfide to yield sulfmyoglobin. Horse heart myoglobin, void of cysteine, was used to avoid possible interference from protein thiols. For aqueous solution, the reactions were found to be second-order, and an apparent acid catalysis could be quantitatively accounted for in terms of a fast reaction between protonated ferrylmyoglobin, MbFe(IV)=O,H+, and hydrogen sulfide, H2S (k(2) = (2.5 +/- 0.1) X 10(6) L mol(-1) s(-1) for 25.0 degrees C, ionic strengh 0.067, dominating for pH < 4), and a slow reaction between MbFe(IV)=O and HS- (k(2) = (1.0 +/- 0.7) x 10(4) L mol(-1) s(-1) for 25.0 degrees C, ionic strengh 0.067, dominating for pH > 7). For meat pH, a reaction via the transition state [MbFe(IV)=O center dot center dot center dot H center dot center dot center dot HS](double dagger) contributed significantly, and this reaction appeared almost independent of temperature with an apparent energy of activation of 2.1 +/- 0.7 kJ mol(-1) at pH 7.4, as a result of compensation among activation energies and temperature influence on pK(a) values explaining low temperature greening of meat. (AU)

• Processo FAPESP: 11/51555-7 - Pão e carne para o futuro
• Beneficiário: Daniel Rodrigues Cardoso
• Modalidade de apoio: Auxílio à Pesquisa - Regular