scholarly journals Enzymic conversion of α-oxyprotohaem IX into biliverdin IXα by haem oxygenase

1990 ◽  
Vol 270 (3) ◽  
pp. 659-664 ◽  
Author(s):  
T Yoshinaga ◽  
Y Sudo ◽  
S Sano
Keyword(s):  
Cytochrome C ◽  
Kinetic Study ◽  
Maximum Velocity ◽  
Incubation Mixture ◽  
Biliverdin Reductase ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Haem Oxygenase ◽  
Biliverdin Ix ◽  
Nadph Cytochrome C Reductase

Conversion of four isomers of meso-oxyprotohaem IX into the corresponding biliverdin IX was attempted with a reconstituted haem oxygenase system in the presence of NADPH-cytochrome c reductase and NADPH. Only the alpha-isomer of meso-oxyprotohaem IX was converted effectively into biliverdin IX alpha, which was further reduced to bilirubin IX alpha by biliverdin reductase. Only trace amounts of biliverdins IX beta, IX gamma and IX delta were respectively formed from the incubation mixture of the corresponding oxyprotohaemin IX isomers with the complete haem oxygenase system under the same conditions. In a kinetic study, the Km for alpha-meso-oxyprotohaem IX was 3.6 microM, which was 2-fold higher than that for protohaem IX. The maximum velocity (Vmax.) of the conversion of alpha-meso-oxyprotohaem IX into biliverdin IX alpha was twice as fast as that of protohaem IX. These results demonstrate that alpha-meso-oxyprotohaem IX is an intermediate of haem degradation and it was converted stereospecifically into biliverdin IX alpha via verdohaem IX alpha.

scholarly journals Electron-transport pathway of the NADH-dependent haem oxygenase system of rat liver microsomal fraction induced by cobalt chloride

1979 ◽  
Vol 178 (2) ◽  
pp. 323-329 ◽  
Author(s):  
Y Hino ◽  
S Minakami
Keyword(s):  
Cytochrome C ◽  
Rat Liver ◽  
Microsomal Fraction ◽  
Cytochrome B5 ◽  
Transport Pathway ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Haem Oxygenase ◽  
Reported Data ◽  
Nadph Cytochrome C Reductase

The hepatic microsomal haem oxygenase activity of rats treated with CoCl2 was studied kinetically by measuring biliverdin, the immediate product of the reaction. Biliverdin was extracted with diethyl ether/ethanol mixture, and was determined by the difference between A690 and A800. The apparent Km value for NADPH (at 50 microM-haematin) was about 0.2 microM when an NADPH-generating system was used, whereas that for NADH was about 630 microM. Essentially the same Vmax. values were obtained for both the NADH- and NADPH-dependent haem oxygenase reactions. No synergism was observed with NADH and NADPH. The NADH-dependent reaction was competitively inhibited by NADP+, with a Ki of about 10 microM. The inhibitoin of the NADH-dependent reaction by the antibody against rat liver microsomal NADPH-cytochrome c reductase was essentially complete, with a pattern similar to that of the NADPH-dependent reaction. The immunochemical experiment and the comparison of the kinetic values with the reported data on isolated NADH-cytochrome b5 reductase and NADPH–cytochrome c reductase indicated the involvement of the latter enzyme in NADH-dependent haem oxygenation by microsomal fraction in situ.

scholarly journals Topological arrangement in microsomal membranes of hepatic haem oxygenase induced by cobalt chloride

1979 ◽  
Vol 178 (2) ◽  
pp. 331-337 ◽  
Author(s):  
Y Hino ◽  
H Asagami ◽  
S Minakami
Keyword(s):  
Cytochrome C ◽  
Time Course ◽  
Reductase Activity ◽  
Microsomal Preparation ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Oxygenase Activity ◽  
Microsomal Membranes ◽  
Haem Oxygenase ◽  
Nadph Cytochrome C Reductase

1. The microsomal haem oxygenase activity induced by the administration of CoCl2 was found mainly in the smooth-surfaced microsomal fraction, whereas that of the untreated control animals was widely distributed in smooth-surfaced microsomal, rough-surfaced microsomal and Golgi fractions. 2. When microsomal preparation was incubated and the time course of the distribution of biliverdin between the membranes and the medium was followed, most of the biliverdin formed was found first in the medium. This suggests that the active site of haem oxygenase is exposed on the cytoplasmic surface of the membranes. The possible localization of the enzyme at the outer surface of the membranes was also supported by a digestion experiment with trypsin. The haem oxygenase activity was greatly decreased even at low concentration of the proteinase, which did not affected the NADPH-cytochrome c reductase activity. 3. When microsomal preparation was further fractionated by isopycnic centrifugation in the presence of deoxycholate or by partitioning of sonicated microsomal preparation in aqueous-polymer two-phase systems, most of the haem oxygenase activity was found in a fraction different from the main fraction of the NADH- and NADPH-cytochrome c reductase and NADH–ferricyanide reductase activities. This indicates the different distribution of haem oxygenase from the other enzymes mentioned, on the lateral plane of microsomal membranes, and suggests the different localization of the haem oxygenase system from the electron-transport system linked with cytochrome b5 and cytochrome P-450.

scholarly journals Étude de l’effet du cadmium et du benzo[a]pyrène sur des enzymes de phase I et phase II de biotransformation chez le polychète Nereisdiversicolor

2009 ◽  
Vol 22 (3) ◽  
pp. 451-459
Author(s):  
Zied Bouraoui ◽  
Jihene Ghedira ◽  
Jamel Jebali ◽  
Mohamed Banni ◽  
Cristelle Clerendeau ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Phase I ◽  
Phase Ii ◽  
Nereis Diversicolor ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Nadph Cytochrome C Reductase

Résumé Le présent travail reporte l’effet du cadmium (Cd), du benzo[a]pyrène (B[a]P) ainsi que leur mélange (Cd/B[a]P), à 1 µM, sur les activités d’enzymes impliqués dans la phase I et la phase II de biotransformation chez le polychète Nereis diversicolor en fonction du temps (après 12, 24, 36 et 48 h). L’effet d’une contamination aiguë par du cadmium à une dose de 1 µM après 12, 24 et 36 h montre une inhibition de l’activité NADPH cytochrome C réductase chez les individus contaminés comparés à leurs témoins relatifs, alors que le seul effet du cadmium sur l’activité glutathion-S-transférase n’est enregistré qu’après 36 h d’exposition. Quant au benzo[a]pyrène, les résultats montrent une augmentation significative de l’activité NADPH cytochrome C réductase après 12, 24 et 36 h d’exposition, alors que pour l’activité glutathion-S‑transférase, la variation significative entre les animaux témoins et traités n’est enregistrée qu’à 36 h d’exposition. Le mélange (Cd/B[a]P) inhibe l’activité NADPH cytochrome C réductase chez les individus traités par comparaison aux témoins relatifs et montre un effet inducteur sur l’activité GST sauf après 36 h d’exposition. Ces résultats montrent ainsi les interactions entre les polluants ainsi que leurs effets sur les organismes.

Sign in / Sign up

Export Citation Format

Share Document