Mutagenic activation of 2-acetylaminofluorene by guinea-pig liver homogenates: Essential involvement of cytochrome P-450 mixed-function oxidases

1979 ◽  
Vol 62 (3) ◽  
pp. 425-437 ◽  
Author(s):  
Keiichi Takeishi ◽  
Sumiko Okuno-Kaneda ◽  
Takeshi Seno
Keyword(s):  
Guinea Pig ◽  
Pig Liver ◽  
Mixed Function Oxidases ◽  
Liver Homogenates ◽  
Cytochrome P 450 ◽  
Guinea Pig Liver

scholarly journals An oxygenase from guinea-pig liver which catalyses sulphoxidation

1974 ◽  
Vol 143 (3) ◽  
pp. 613-624 ◽  
Author(s):  
Kumaraswamy Prema ◽  
K. P. Gopinathan
Keyword(s):  
Guinea Pig ◽  
Maximal Activity ◽  
Superoxide Anions ◽  
Optimal Conditions ◽  
Metabolizing Enzymes ◽  
Pig Liver ◽  
General Drug ◽  
Liver Homogenates ◽  
Cytochrome P 450 ◽  
Guinea Pig Liver

A mono-oxygenase catalysing the conversion of 2-ethyl-4-thioisonicotinamide (ethionamide) into its sulphoxide was purified from guinea-pig liver homogenates. The enzyme required stoicheiometric amounts of oxygen and NADPH for the sulphoxidation reaction. The purified protein is homogeneous by electrophoretic, antigenic and chromatographic criteria. The enzyme has mol.wt. 85000 and it contains 1g-atom of iron and 1mol of FAD per mol, but not cytochrome P-450. The enzyme shows maximal activity at pH7.4 in a number of different buffer systems and the Km values calculated for the substrate and NADPH are 6.5×10−5m and 2.8×10−5m respectively. The activation energy of the reaction was calculated to be 36kJ/mol. Under optimal conditions, the molecular activity of the enzyme (mol of substrate oxidized/min per mol of enzyme) is calculated to be 2.1. The oxygenase belongs to the class of general drug-metabolizing enzymes and it may act on different compounds which can undergo sulphoxidation. The mechanism of sulphoxidation was shown to be mediated by superoxide anions.

Die Bedeutung der Homogenisationsart und -intensität für die Größe und Konstanz der Sauerstoffaufnahme von Meerschweinchen-Leberhomogenat / The Influence of Mode and Intensity of Homogenization on the Absolute Value and Stability of Oxygen Consumption of Guinea Pig Liver Homogenates

1977 ◽  
Vol 32 (11-12) ◽  
pp. 908-912 ◽  
Author(s):  
H. J. Schmidt ◽  
U. Schaum ◽  
J. P. Pichotka
Keyword(s):  
Oxygen Uptake ◽  
Guinea Pig ◽  
Measuring Time ◽  
Pig Liver ◽  
Absolute Value ◽  
Modified Method ◽  
Simultaneous Measurements ◽  
Liver Homogenates ◽  
The Absolute ◽  
Guinea Pig Liver

Abstract The influence of five different methods of homogenisation (1. The method according to Potter and Elvehjem, 2. A modification of this method called Potter S, 3. The method of Dounce, 4. Homogenisation by hypersonic waves and 5. Coarce-grained homogenisation with the “Mikro-fleischwolf”) on the absolute value and stability of oxygen uptake of guinea pig liver homogenates has been investigated in simultaneous measurements. All homogenates showed a characteristic fall of oxygen uptake during measuring time (3 hours). The modified method according to Potter and Elvehjem called Potter S showed reproducible results without any influence by homogenisation intensity.

scholarly journals COMPARISONS OF THE OXIDATION OF C19-HYDROXYSTEROIDS BY GUINEA PIG LIVER HOMOGENATES

1957 ◽  
Vol 224 (2) ◽  
pp. 811-818
Author(s):  
Charles D. Kochakian ◽  
Betty R. Carroll ◽  
Barbara Uhri
Keyword(s):  
Guinea Pig ◽  
Pig Liver ◽  
Liver Homogenates ◽  
Guinea Pig Liver

Glucosiduronidation of 15α-hydroxyestrogens by guinea pig liver homogenates

Steroids ◽  
1972 ◽  
Vol 19 (4) ◽  
pp. 535-547 ◽  
Author(s):  
H. Jirku ◽  
S. Kadner ◽  
M. Levitz
Keyword(s):  
Guinea Pig ◽  
Pig Liver ◽  
Liver Homogenates ◽  
Guinea Pig Liver

scholarly journals Photoaffinity labelling of nucleoside-transport proteins in plasma membranes isolated from rat and guinea-pig liver

1984 ◽  
Vol 220 (2) ◽  
pp. 499-506 ◽  
Author(s):  
J S R Wu ◽  
J D Young
Keyword(s):  
Guinea Pig ◽  
Plasma Membranes ◽  
Species Difference ◽  
Sodium Dodecyl ◽  
Competitive Inhibitor ◽  
Nucleoside Transport ◽  
Nucleoside Transporter ◽  
Pig Liver ◽  
Liver Homogenates ◽  
Guinea Pig Liver

Nitrobenzylthioinosine (NBMPR) was employed as a probe of the nucleoside transporters from rat and guinea-pig liver. Purified liver plasma membranes prepared on self-generating Percoll density gradients exhibited 16-fold (rat) and 10-fold (guinea pig) higher [3H]NBMPR-binding activities than in crude liver homogenates (3.69 and 14.7 pmol/mg of protein for rat and guinea-pig liver membranes respectively, and 0.23 and 1.47 pmol/mg of protein for crude liver homogenates respectively). Binding to membranes from both species was saturable (apparent Kd 0.14 and 0.63 nM for rat and guinea-pig membranes respectively) and inhibited by uridine, adenosine, nitrobenzylthioguanosine (NBTGR) and dilazep. Uridine was an apparent competitive inhibitor of high-affinity NBMPR binding to rat membranes (apparent Ki 1.5 mM). There was a marked species difference with respect to dipyridamole inhibition of NBMPR binding (50% inhibition at 0.2 and greater than 100 microM for guinea-pig and rat respectively). These results are consistent with a role of NBMPR-binding proteins in liver nucleoside transport. Exposure of rat and guinea pig membranes to high-intensity u.v. light in the presence of [3H]NBMPR resulted in the selective radio-labelling of membrane proteins which migrated on sodium dodecyl sulphate/polyacrylamide gels with apparent Mr values in the same range as that of the human erythrocyte nucleoside transporter (45 000-66 000). Covalent labelling of these proteins was abolished when photolysis was performed in the presence of non-radio-active NBTGR as competing ligand.

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