The effect of o-diphenols upon the microsomal NADPH and NADH oxidase activities

Augusto, Ohára; Bechara, Etelvino J.H.; Sanioto, Divo L.; Cilento, Giuseppe

doi:10.1016/0003-9861(73)90632-2

Cited by 16 publications

(2 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This mechanism is in agreement with recent findings of Augusto et al 23, who reported that microsomal oxidation of NADPH is stimulated by epinephrine. This stimulation is suppressed by SDM, however, if this enzyme is added before the reaction is started.…”

Section: IIIsupporting

confidence: 94%

Involvement of the Superoxide Free Radical Ion in Photosynthetic Oxygen Reduction

Elstner

Heupel

1974

Zeitschrift Für Naturforschung C

View full text Add to dashboard Cite

Chloroplasts, Superoxide Radical, Oxygen ReductionPhotosynthetic oxygen reduction by isolated chloroplast lamellar systems has been studied with the aid of superoxide dismutase. Two mechanisms of oxygen reduction by illuminated chloroplast lamellar systems can be differentiated: 1. In the presence of low potential electron acceptors like AQ or MV the superoxide free radical ion is the product of autooxidation of the reduced acceptor. Addition of superoxide dismutase has no influence on the initial rates of oxygen reduction. Stimulation of photosynthetic oxygen reduction by o-diphenols is only observed in the absenceof superoxide dismutase and ascorbate; apparently the superoxide free radical ions is involved in both initiation and propagation of a chain reaction. If the ferredoxin-stimulated photosynthetic oxygen reduction is measured, both ascorbate and superoxide dismutase are active as inhibitors. By heating suspensions of chloroplast lamellar systems, a substance is released into the supernatant which exhibits the activity of an oxygen reducing factor (ORF) with properties similar to o-diphenols: The stimulation of photosynthetic oxygen reduction is reversed by addition of either SDM or ascorbate. A reaction sequence for photosynthetic oxygen reduction in the presence of ferredoxin is considered, which is initiated by the superoxide free radical ion produced by autooxidation of reduced ferredoxin; the superoxide free radical ion "activates" an endogenous oxygen reducing factor, which in this "active" state can reduce oxygen to 0 2"~. The presence of either superoxide dismutase or ascorbate yields in chain termination by scavenging the superoxide free radical ion.

show abstract

Section: IIIsupporting

confidence: 94%

Involvement of the Superoxide Free Radical Ion in Photosynthetic Oxygen Reduction

Elstner

Heupel

1974

Zeitschrift Für Naturforschung C

View full text Add to dashboard Cite

show abstract

“…While measuring NADPH consumption, we found that the addition of cytochrome c or hexobarbital during the reaction of adrenaline oxidation by the microsomal fraction increases the rate of NADPH consumption (Table 5). However, it should be noted that NADPH consumption during the adrenaline oxidation by the microsomal fraction may be related to the stimulating effect of one of the so far unknown products of oxidative conversion of adrenaline (Augusto et al, 1973).…”

Section: Resultsmentioning

confidence: 99%

Relationship between the reduction of oxygen, artificial acceptors and cytochrome P-450 by NADPH-cytochrome c reductase

Lyakhovich¹,

Mishin²,

Pokrovsky³

1977

Biochemical Journal

View full text Add to dashboard Cite

The interaction of NADPH--cytochrome c reductase with oxygen, artificial acceptors and cytochrome P-450 was studied. The generation of superoxide anion radicals (O2-.) from the oxidation of adrenaline to adrenochrome catalysed by NADPH--cytochrome c reductase proceeds independently of the interaction of the enzyme with the artificial anaerobic acceptors cytochrome c or 2,6-dichlorophenol-indophenol. Propyl 3,4,5-trihydroxybenzoate inhibited competitively the adrenaline oxidation by isolated NADPH--cytochrome c reductase (Ki 3.2--4.7 micrometer) and inhibited non-competitively the cytochrome c reduction (Ki 92--109 micrometer). In contrast with the process of electron transfer to cytochrome c, the rate of reduction of cytochrome P-450 and the rate of oxidation of adrenaline in liver microsomal fraction are correlated. Hexobarbital increases the Vmax. of adrenaline oxidation without affecting the Km value, whereas metyrapone, a metabolic inhibitor decreases Vmax. without affecting the Km. From the results obtained, some conclusions about NADPH--cytochrome c reductase function were made.

show abstract