Reductive nitrosylation of ferric cyanide horse heart myoglobin is limited by cyanide dissociation.
Biochem Biophys Res Commun
; 393(2): 196-200, 2010 Mar 05.
Article
en En
| MEDLINE
| ID: mdl-20116365
ABSTRACT
Cyanide binds to ferric heme-proteins with a very high affinity, reflecting the very low dissociation rate constant (k(off)). Since no techniques are available to estimate k(off), we report herewith a method to determine k(off) based on the irreversible reductive nitrosylation reaction to trap ferric myoglobin (Mb(III)). The k(off) value for cyanide dissociation from ferric cyanide horse heart myoglobin (Mb(III)-cyanide) was determined at pH 9.2 and 20.0 degrees C. Mixing Mb(III)-cyanide and NO solutions brings about absorption spectral changes reflecting the disappearance of Mb(III)-cyanide with the concomitant formation of ferrous nitrosylated Mb. Since kinetics of reductive nitrosylation of Mb(III) is much faster than Mb(III)-cyanide dissociation, the k(off) value, representing the rate-limiting step, can be directly determined. The k(off) value obtained experimentally matches very well to that calculated from values of the second-order rate constant (k(on)) and of the dissociation equilibrium constant (K) for cyanide binding to Mb(III) (k(off)=k(on)xK).
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Hemoglobinas
/
Ferricianuros
/
Metamioglobina
/
Miocardio
/
Óxido Nítrico
Límite:
Animals
Idioma:
En
Revista:
Biochem Biophys Res Commun
Año:
2010
Tipo del documento:
Article
País de afiliación:
Italia