scholarly journals The kinetics of rat liver and heart mitochondrial β-hydroxybutyrate dehydrogenase

1979 ◽  
Vol 179 (3) ◽  
pp. 579-581 ◽  
Author(s):  
G A Tucker ◽  
A P Dawson
Keyword(s):  
Rat Liver ◽  
Rat Heart ◽  
Mitochondrial Membrane ◽  
Liver Mitochondria ◽  
Kinetic Constants ◽  
Kinetic Properties ◽  
Kinetic Mechanisms ◽  
Solubilized Enzyme ◽  
Beta Hydroxybutyrate ◽  
Kinetics Of

The kinetic mechanisms of the beta-hydroxybutyrate dehydrogenase from rat heart and liver mitochondria were investigated. Both enzymes, show an Ordered Bi Bi mechanism and there are no major differences in the kinetic constants. In both cases, the solubilized enzyme, re-activated with phosphatidylcholine, shows kinetic properties very similar to those of the enzyme bound to the mitochondrial membrane.

scholarly journals Uptake of protoporphyrin IX by isolated rat liver mitochondria

1980 ◽  
Vol 188 (2) ◽  
pp. 329-335 ◽  
Author(s):  
M E Koller ◽  
I Romslo
Keyword(s):  
Rat Liver ◽  
Mitochondrial Membrane ◽  
Protoporphyrin Ix ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Erythropoietic Protoporphyria ◽  
Inner Membrane ◽  
Isolated Rat Liver ◽  
Isolated Rat

Rat liver mitochondria accumulate protoporphyrin IX from the suspending medium into the inner membrane in parallel with the magnitude of the transmembrane K+ gradient (K+in/K+out). Only protoporphyrin IX taken up in parallel with the transmembrane K+ gradient is available for haem synthesis. Coproporphyrins (isomers I and III) are not taken up by the mitochondria. The results support the suggestion by Elder & Evans [(1978) Biochem. J. 172, 345-347] that the prophyrin to be taken up by the inner mitochondrial membrane belongs to the protoporphyrin(ogen) IX series. Protoporphyrin IX at concentrations above 15 nmol/mg of protein has detrimental effects on the structural and functional integrity of the mitochondria. The relevance of these effects to the hepatic lesion in erythropoietic protoporphyria is discussed.

scholarly journals Quantitative characteristics of glutamate transport in rat liver mitochondria

1973 ◽  
Vol 134 (4) ◽  
pp. 1023-1029 ◽  
Author(s):  
Norah M. Bradford ◽  
J. D. McGivan
Keyword(s):  
Rat Liver ◽  
Transport Process ◽  
Liver Mitochondria ◽  
Glutamate Transport ◽  
Rat Liver Mitochondria ◽  
Bromocresol Purple ◽  
Quantitative Characteristics ◽  
Kinetics Of

1. The kinetics of glutamate transport into mitochondria were determined by using Bromocresol Purple to terminate the transport process. 2. Glutamate transport was found to have a Vmax. of 9.1nmol/min per mg of protein at pH6.9 and 20°C; the Km for glutamate was 4mm. 3. The rate of glutamate deamination in intact mitochondria was tenfold slower than in disrupted mitochondria. 4. These results suggest that glutamate deamination may be controlled by the rate of glutamate transport. Possible consequences of these findings are discussed.

Kinetics of calcium(2+) ion carrier in rat liver mitochondria

Biochemistry ◽  
1979 ◽  
Vol 18 (26) ◽  
pp. 5972-5978 ◽  
Author(s):  
Marco Bragadin ◽  
Tullio Pozzan ◽  
Giovanni Felice Azzone
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Ion Carrier ◽  
Kinetics Of

Multiple monoamine oxidases in rat liver mitochondria

1970 ◽  
Vol 48 (6) ◽  
pp. 659-663 ◽  
Author(s):  
L. Sierens ◽  
A. D'Iorio
Keyword(s):  
Rat Liver ◽  
Indirect Evidence ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Electrophoretic Separation ◽  
Oxidative Deamination ◽  
Monoamine Oxidases ◽  
Kinetics Of

Indirect evidence from the kinetics of oxidative deamination is presented for the existence of two different monoamine oxidases in rat liver mitochondria. The enzymes can be differentiated on the basis of their affinities for benzylamine and serotonin. Electrophoretic separation yielded two fractions, each with the characteristics predicted from the kinetic experiments.

scholarly journals The control of isocitrate oxidation by rat liver mitochondria

1969 ◽  
Vol 114 (2) ◽  
pp. 215-225 ◽  
Author(s):  
D. G. Nicholls ◽  
P. B. Garland
Keyword(s):  
Respiratory Chain ◽  
Rat Liver ◽  
Isocitrate Dehydrogenase ◽  
Adenine Nucleotides ◽  
Kinetic Studies ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Kinetic Properties ◽  
Dependent Inhibition ◽  
Nad 4

1. The factors capable of affecting the rate of isocitrate oxidation in intact mitochondria include the rate of isocitrate penetration, the activity of the NAD-specific and NADP-specific isocitrate dehydrogenases, the activity of the transhydrogenase acting from NADPH to NAD+, the rate of NADPH oxidation by the reductive synthesis of glutamate and the activity of the respiratory chain. A quantitative assessment of these factors was made in intact mitochondria. 2. The kinetic properties of the NAD-specific and NADP-specific isocitrate dehydrogenases extracted from rat liver mitochondria were examined. 3. The rate of isocitrate oxidation through the respiratory chain in mitochondria with coupled phosphorylation is approximately equal to the maximal of the NAD-specific isocitrate dehydrogenase but at least ten times as great as the transhydrogenase activity from NADPH to NAD+. 4. It is concluded that the energy-dependent inhibition of isocitrate oxidation by palmitoylcarnitine oxidation is due to an inhibition of the NAD-specific isocitrate dehydrogenase. 5. Kinetic studies of NAD-specific isocitrate dehydrogenase demonstrated that its activity could be inhibited by one or more of the following: an increased reduction of mitochondrial NAD, an increased phosphorylation of mitochondrial adenine nucleotides or a fall in the mitochondrial isocitrate concentration. 6. Uncoupling agents stimulate isocitrate oxidation by an extent equal to the associated stimulation of transhydrogenation from NADPH to NAD+. 7. A technique is described for continuously measuring with a carbon dioxide electrode the synthesis of glutamate from isocitrate and ammonia.

scholarly journals The maturation of the inner membrane of foetal rat liver mitochondria. An example of a positive-feedback mechanism

1975 ◽  
Vol 150 (3) ◽  
pp. 477-488 ◽  
Author(s):  
J K Pollak
Keyword(s):  
Oxidative Phosphorylation ◽  
Rat Liver ◽  
Mitochondrial Membrane ◽  
Respiratory Control ◽  
Liver Mitochondria ◽  
Neonatal Rat ◽  
Rat Liver Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Mature Adult ◽  
Foetal Rat

A new method was devised for the isolation of foetal and neonatal rat lvier mitochondria, giving higher yields than conventional methods. 2. During development from the perinatal period to the mature adult, the ratio of cytochrome oxidase/succinate-cytochrome c reductase changes. 3. The inner mitochondrial membrane of foetal liver mitochondria possesses virtually no osmotic activity; the permeability to sucrose decreases with increasing developmental age. 4. Foetal rat liver mitochondria possess only marginal respiratory control and do not maintain Ca2+-induced respiration; they also swell in respiratory-control medium in the absence of substrate. ATP enhances respiratory control and prevents swelling, adenylyl imidodiphosphate, ATP+atractyloside enhance the R.C.I. (respiratory control index), Ca2+-induced respiratory control and prevent swelling, whereas GTP and low concentrations of ADP have none of these actions. It is concluded that the effect of ATP depends on steric interaction with the inner mitochondrial membrane. 5. When 1-day pre-partum foetuses are obtained by Caesarean section and maintained in a Humidicrib for 90 min, mitochondrial maturation is ‘triggered’, so that their R.C.I. is enhanced and no ATP is required to support Ca2+-dependent respiratory control or to inhibit mitochondrial swelling. 6. It is concluded that foetal rat liver mitochondria in utero do not respire, although they are capable of oxidative phosphorylation in spite of their low R.C.I. The different environmental conditions which the neonatal rat encounters ex utero enable the hepatic mitochondria to produce ATP, which interacts with the inner mitochondrial membrane to enhance oxidative phosphorylation by an autocatalytic mechanism.

Sign in / Sign up

Export Citation Format

Share Document