The reactivity of myeloperoxidase compound I formed with hypochlorous acid.
Redox Rep
; 5(4): 173-8, 2000.
Article
en En
| MEDLINE
| ID: mdl-10994870
The reaction of human myeloperoxidase (MPO) with hypochlorous acid (HOCl) was investigated by conventional stopped-flow spectroscopy at pH 5, 7, and 9. In the reaction of MPO with HOCl, compound I is formed. Its formation is strongly dependent on pH. HOCl (rather than OCl-) reacts with the unprotonated enzyme in its ferric state. Apparent second-order rate constants were determined to be 8.1 x 10(7) M(-1)s(-1) (pH 5), 2.0 x 10(8) M(-1)s(-1) (pH 7) and 2.0 x 10(6) M(-1)s(-1) (pH 9) at 15 degrees C. Furthermore, the kinetics and spectra of the reactions of halides and thiocyanate and of physiologically relevant one-electron donors (ascorbate, nitrite, tyrosine and hydrogen peroxide) with this compound I were investigated using the sequential-mixing technique. The results show conclusively that the redox intermediates formed upon addition of either hydrogen peroxide or hypochlorous acid to native MPO exhibit the same spectral features and reactivities and thus are identical. In stopped-flow investigations, the MPO/HOCl system has some advantage since: (i) in contrast to H2O2, HOCl cannot function as a one-electron donor of compound I; and (ii) MPO can easily be prevented from cycling by addition of methionine as HOCl scavenger. As a consequence, the observed absorbance changes are bigger and errors in data analysis are smaller.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Ácido Hipocloroso
/
Peroxidasa
Límite:
Humans
Idioma:
En
Revista:
Redox Rep
Asunto de la revista:
BIOQUIMICA
/
METABOLISMO
Año:
2000
Tipo del documento:
Article
País de afiliación:
Austria
Pais de publicación:
Reino Unido