The enzymic reduction and kinetics of oxidation of cytochrome b-245 of neutrophils.
Biochem J
; 204(2): 479-85, 1982 May 15.
Article
en En
| MEDLINE
| ID: mdl-7115343
ABSTRACT
1. The absorption coefficient of human neutrophil plasma-membrane reduced-minus-oxidized cytochrome b-245 was determined [delta epsilon (mM; 559-540 nm) = 21.6 cm-1]. 2. Neutrophil polymorphonuclear leucocytes (neutrophils) were prepared from human, ox, horse and pig blood. In each case plasma-membrane fractions were found to contain low-potential cytochrome b. When membranes from horse neutrophils were incubated anaerobically with either NADH or NADPH the cytochrome b became reduced. Prior stimulation of the cells with phorbol myristate acetate did not increase the rate or extent of cytochrome b reduction in isolated membranes, but did increase both the rate and extent of reduction by NADPH in Triton-treated cells. 3. A cytochrome b was present also in the specific granule fraction of human neutrophils. Its Em (pH 7.0) was found to be -248 mV, very similar to that of the plasma-membrane cytochrome b. 4. The rate of oxidation of reduce cytochrome b-245 by air-saturated buffer, was determined by using stopped-flow techniques. In intact membranes t 1/2 for oxidation was 4.7 ms. This rate is sufficiently rapid to support the view that cytochrome b-245 is the oxidase in the respiratory burst of neutrophils. 5. Plasma-membrane cytochrome b of human neutrophils formed a complex with CO. At room temperature and 1 atm of CO approx. 40% of the cytochrome formed a complex; approx. 60% binding was measured at the increased concentration of dissolved CO achieved at 5 degrees C. The concentration of CO giving 50% binding was 1.18 mM.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Grupo Citocromo b
/
Citocromos
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Neutrófilos
Límite:
Animals
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Humans
Idioma:
En
Revista:
Biochem J
Año:
1982
Tipo del documento:
Article
Pais de publicación:
ENGLAND
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ESCOCIA
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GB
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GREAT BRITAIN
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INGLATERRA
/
REINO UNIDO
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SCOTLAND
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UK
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UNITED KINGDOM