scholarly journals Treatment of rats with glucagon or mannoheptulose increases mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity and decreases succinyl-CoA content in liver

1989 ◽  
Vol 262 (1) ◽  
pp. 159-164 ◽  
Author(s):  
P A Quant ◽  
P K Tubbs ◽  
M D Brand
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Ketone Bodies ◽  
Liver Mitochondria ◽  
Mitochondrial Activity ◽  
Acetyl Coa ◽  
Total Enzyme Activity ◽  
Liver Homogenates ◽  
Rat Livers ◽  
Total Enzyme

1. The activity of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (EC 4.1.3.5) in extracts of rapidly frozen rat livers was doubled in animals treated in various ways to increase ketogenic flux. 2. Some 90% of the activity measured was mitochondrial, and changes in mitochondrial activity dominated changes in total enzyme activity. 3. The elevated HMG-CoA synthase activities persisted throughout the isolation of liver mitochondria. 4. Intramitochondrial succinyl-CoA content was lower in whole liver homogenates and in mitochondria isolated from animals treated with glucagon or mannoheptulose. 5. HMG-CoA synthase activity in mitochondria from both ox and rat liver was negatively correlated with intramitochondrial succinyl-CoA levels when these were manipulated artificially. Under these conditions, the differences between mitochondria from control and hormone-treated rats were abolished. 6. These findings show that glucagon can decrease intramitochondrial succinyl-CoA concentration, and that this in turn can regulate mitochondrial HMG-CoA synthase. They support the hypothesis that the formation of ketone bodies from acetyl-CoA may be regulated by the extent of succinylation of mitochondrial HMG-CoA synthase.

scholarly journals Acetyl-coenzyme A deacylase activity in liver is not an artifact. Subcellular distribution and substrate specificity of acetyl-coenzyme A deacylase activities in rat liver

1979 ◽  
Vol 177 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Klaus-P. Grigat ◽  
Klaus Koppe ◽  
Claus-D. Seufert ◽  
Hans-D Söling
Keyword(s):  
Rat Liver ◽  
Coenzyme A ◽  
Liver Mitochondria ◽  
Acid Oxidation ◽  
Matrix Space ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Lysosomal Fraction ◽  
Total Enzyme Activity ◽  
Acetyl Coenzyme

Whole liver and isolated liver mitochondria are able to release free acetate, especially under conditions of increased fatty acid oxidation. In the present paper it is shown that rat liver contains acetyl-CoA deacylase (EC 3.1.2.1) activity (0.72μmol/min per g wet wt. of liver at 30°C and 0.5mm-acetyl-CoA). At 0.5mm-acetyl-CoA 73% of total enzyme activity was found in the mitochondria, 8% in the lysosomal fraction and 19% in the postmicrosomal supernatant. Mitochondrial subfractionation shows that mitochondrial acetyl-CoA deacylase activity is restricted to the matrix space. Mitochondrial acetyl-CoA deacylase showed almost no activity with either butyryl- or hexanoyl-CoA. Acetyl-CoA hydrolase activity from purified rat liver lysosomes exhibited a very low affinity for acetyl-CoA (apparent Km>15mm compared with an apparent Km value of 0.5mm for the mitochondrial enzyme) and reacted at about the same rate with acetyl-, n-butyryl- and hexanoyl-CoA. We could not confirm the findings of Costa & Snoswell [(1975) Biochem. J.152, 167–172] according to which mitochondrial acetyl-CoA deacylase was considered to be an artifact resulting from the combined actions of acetyl-CoA–l-carnitine acetyltransferase (EC 2.3.1.7) and acetylcarnitine hydrolase. The results are in line with the concept that free acetate released by the liver under physiological conditions stems from the intramitochondrial deacylation of acetyl-CoA.

scholarly journals Growth-hormone-prolactin interactions in the regulation of mammary and adipose-tissue acetyl-CoA carboxylase activity and gene expression in lactating rats

1992 ◽  
Vol 285 (2) ◽  
pp. 469-475 ◽  
Author(s):  
M C Barber ◽  
M T Travers ◽  
E Finley ◽  
D J Flint ◽  
R G Vernon
Keyword(s):  
Adipose Tissue ◽  
Mammary Gland ◽  
Serum Prolactin ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Carboxylase Activity ◽  
Total Enzyme Activity ◽  
Mrna Concentration ◽  
Total Enzyme ◽  
Activation Status

The factors and mechanisms responsible for the reciprocal changes in lipogenesis in rat mammary gland and adipose tissue during the lactation cycle have been investigated. Lactation decreased the activation status and mRNA concentration of acetyl-CoA carboxylase in adipose tissue. Litter removal decreased the mRNA concentration of acetyl-CoA carboxylase in the mammary gland and increased the enzyme's mRNA concentration and activation status in adipose tissue. Lowering serum prolactin concentration in lactating rats decreased the amount of mammary acetyl-CoA carboxylase mRNA and increased that of adipose tissue, and increased the activation status of the enzyme in adipose tissue. Decreasing serum growth hormone (GH) alone had little effect on acetyl-CoA carboxylase in lactating rats, although it did lower pup growth rate and serum concentration of insulin-like growth factor-I. Lowering serum GH concentration exacerbated the effects of decreasing serum prolactin on mammary-gland (but not adipose-tissue) acetyl-CoA carboxylase mRNA and further increased the rise in activation status of the adipose-tissue enzyme induced by decreasing serum prolactin. Changes in acetyl-CoA carboxylase mRNA in both mammary and adipose tissue were paralleled by changes in total enzyme activity except after litter removal, when there was a disproportionately large decrease in total enzyme activity of the mammary gland. Thus prolactin has a major and GH a minor role in the regulation of acetyl-CoA carboxylase activity during lactation. Changes in mammary activity in response to prolactin and GH are primarily due to alterations in gene transcription, whereas adaptation in adipose tissue involves both changes in gene transcription and activation status.

scholarly journals Two-Step Production of Neofructo-Oligosaccharides Using Immobilized Heterologous Aspergillus terreus 1F-Fructosyltransferase Expressed in Kluyveromyces lactis and Native Xanthophyllomyces dendrorhous G6-Fructosyltransferase

Catalysts ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 673 ◽  
Author(s):  
Burghardt ◽  
Baas ◽  
Gerlach ◽  
Czermak
Keyword(s):  
Response Surface Methodology ◽  
Enzyme Activity ◽  
Reaction Time ◽  
Aspergillus Terreus ◽  
Kluyveromyces Lactis ◽  
Xanthophyllomyces Dendrorhous ◽  
Initial Concentration ◽  
Total Enzyme Activity ◽  
Glycosidic Bonds ◽  
Total Enzyme

Fructo-oligosaccharides (FOS) are prebiotic low-calorie sweeteners that are synthesized by the transfer of fructose units from sucrose by enzymes known as fructosyltransferases. If these enzymes generate β-(2,6) glycosidic bonds, the resulting oligosaccharides belong to the neoseries (neoFOS). Here, we characterized the properties of three different fructosyltransferases using a design of experiments approach based on response surface methodology with a D-optimal design. The reaction time, pH, temperature, and substrate concentration were used as parameters to predict three responses: The total enzyme activity, the concentration of neoFOS and the neoFOS yield relative to the initial concentration of sucrose. We also conducted immobilization studies to establish a cascade reaction for neoFOS production with two different fructosyltransferases, achieving a total FOS yield of 47.02 ± 3.02%. The resulting FOS mixture included 53.07 ± 1.66 mM neonystose (neo-GF3) and 20.8 ± 1.91 mM neo-GF4.

scholarly journals The effects of starvation and experimental diabetes on phosphoenol-pyruvate carboxykinase in the guinea pig

1977 ◽  
Vol 164 (2) ◽  
pp. 357-361 ◽  
Author(s):  
K R F Elliott ◽  
C I Pogson
Keyword(s):  
Enzyme Activity ◽  
Guinea Pig ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Blood Glucose Concentration ◽  
Mitochondrial Fraction ◽  
Kidney Cortex ◽  
Total Enzyme Activity ◽  
The Mean ◽  
Mean Blood Glucose ◽  
Total Enzyme

1. Approx. 85% of liver phosphoenolpyruvate carboxykinase is associated with the mitochondrial fraction in the fed guinea pig. Enzyme activity is unchanged in diabetes, but doubles during starvation. In contrast with earlier reports, both cytoplasmic and mitochondrial activities were found to be increased. 2. In kidney cortex, total enzyme activity is increased in both starved and diabetic animals. These changes are associated with increases in the cytoplasmic activity alone. 3. In diabetic animals the mean blood-glucose concentration was 23.1 mM. Other blood metabolites were lower than those in the rat, and the animals did not show significant ketosis. 4. Changes in the rates of gluconeogenesis from lactate and propionate paralleled those in phosphoenolpyruvate carboxykinase activity.

Changes in mass and catalytic activity concentrations of aspartate aminotransferase isoenzymes in serum after a myocardial infarction.

1986 ◽  
Vol 32 (3) ◽  
pp. 496-500 ◽  
Author(s):  
A E Niblock ◽  
G Jablonsky ◽  
F Y Leung ◽  
A R Henderson
Keyword(s):  
Myocardial Infarction ◽  
Enzyme Activity ◽  
Catalytic Activity ◽  
Aspartate Aminotransferase ◽  
Left Ventricular ◽  
Peak Activity ◽  
Ventricular Failure ◽  
Total Enzyme Activity ◽  
Activity Concentrations ◽  
Total Enzyme

Abstract We used an RIA and inhibition of enzyme activity to monitor the changes in mass and catalytic concentrations of the aspartate aminotransferase (EC 2.6.1.1;AST) isoenzymes in serum after myocardial infarction. Cytosolic (c-AST) and mitochondrial (m-AST) forms of AST were present in sera from all 38 of our patients. Although the immunological and catalytic concentrations of both isoenzymes correlated well with the size of the infarct, c-AST gave a better measure than did m-AST. About 20% of the total enzyme activity at peak activity was from the mitochondrial isoenzyme. Both isoenzyme activities peak at very nearly the same time, but m-AST has the longer half-life. Immunological evidence of the mitochondrial isoenzyme can be detected in serum for at least eight days after the infarct. The presence of left ventricular failure produces greater serum isoenzyme activities than in those without failure.

scholarly journals Hepatic ketogenesis in newborn pigs is limited by low mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity

1994 ◽  
Vol 298 (1) ◽  
pp. 207-212 ◽  
Author(s):  
P H Duée ◽  
J P Pégorier ◽  
P A Quant ◽  
C Herbin ◽  
C Kohl ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Oxidation Products ◽  
Rat Liver Mitochondria ◽  
Acid Oxidation ◽  
Acetyl Coa ◽  
Pig Liver ◽  
Adult Rat ◽  
Malonyl Coa ◽  
Cpt I

In newborn-pig hepatocytes, the rate of oleate oxidation is extremely low, despite a very low malonyl-CoA concentration. By contrast, the sensitivity of carnitine palmitoyltransferase (CPT) I to malonyl-CoA inhibition is high, as suggested by the very low concentration of malonyl-CoA required for 50% inhibition of CPT I (IC50). The rates of oleate oxidation and ketogenesis are respectively 70 and 80% lower in mitochondria isolated from newborn-pig liver than from starved-adult-rat liver mitochondria. Using polarographic measurements, we showed that the oxidation of oleoyl-CoA and palmitoyl-L-carnitine is very low when the acetyl-CoA produced is channelled into the hydroxymethylglutaryl-CoA (HMG-CoA) pathway by addition of malonate. In contrast, the oxidation of the same substrates is high when the acetyl-CoA produced is directed towards the citric acid cycle by addition of malate. We demonstrate that the limitation of ketogenesis in newborn-pig liver is due to a very low amount and activity of mitochondrial HMG-CoA synthase as compared with rat liver mitochondria, and suggest that this could promote the accumulation of acetyl-CoA and/or beta-oxidation products that in turn would decrease the overall rate of fatty acid oxidation in newborn- and adult-pig livers.

scholarly journals The kinetic properties of citrate synthase from rat liver mitochondria

1969 ◽  
Vol 114 (3) ◽  
pp. 597-610 ◽  
Author(s):  
D. Shepherd ◽  
P. B. Garland
Keyword(s):  
Rat Liver ◽  
Citrate Synthase ◽  
Adenine Nucleotide ◽  
Sedimentation Coefficient ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Kinetic Properties ◽  
Acetyl Coa ◽  
Ph Optimum ◽  
Michaelis Constants

1. Citrate synthase (EC 4.1.3.7) was purified 750-fold from rat liver. 2. Measurements of the Michaelis constants for the substrates of citrate synthase gave values of 16μm for acetyl-CoA and 2μm for oxaloacetate. Each value is independent of the concentration of the other substrate. 3. The inhibition of citrate synthase by ATP, ADP and AMP is competitive with respect to acetyl-CoA. With respect to oxaloacetate the inhibition by AMP is competitive, but the inhibition by ADP and ATP is mixed, being partially competitive. 4. At low concentrations of both substrates the inhibition by ATP is sigmoidal and a Hill plot exhibits a slope of 2·5. 5. The pH optimum of the enzyme is 8·7, and is not significantly affected by ATP. 6. Mg2+ inhibits citrate synthase slightly, but relieves the inhibition caused by ATP in a complex manner. 7. At constant total adenine nucleotide concentration made up of various proportions of ATP, ADP and AMP, the activity of citrate synthase is governed by the concentration of the sum of the energy-rich phosphate bonds of ADP and ATP. 8. The sedimentation coefficient of the enzyme, as measured by activity sedimentation, is 6·3s, equivalent to molecular weight 95000.

scholarly journals Purification and Partial Characterization of Acetyl-CoA Synthetase in Rat Liver Mitochondria.

2002 ◽  
Vol 48 (5) ◽  
pp. 359-364 ◽  
Author(s):  
Hiromi YAMASHITA ◽  
Akemi FUKUURA ◽  
Tomomi NAKAMURA ◽  
Takao KANEYUKI ◽  
Masumi KIMOTO ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Partial Characterization ◽  
Rat Liver Mitochondria ◽  
Acetyl Coa

scholarly journals Steady-state concentrations of coenzyme A, acetyl-coenzyme A and long-chain fatty acyl-coenzyme A in rat-liver mitochondria oxidizing palmitate

1965 ◽  
Vol 97 (2) ◽  
pp. 587-594 ◽  
Author(s):  
PB Garland ◽  
D Shepherd ◽  
DW Yates
Keyword(s):  
Rat Liver ◽  
Coenzyme A ◽  
Liver Mitochondria ◽  
Fatty Acyl ◽  
Rat Liver Mitochondria ◽  
Beta Oxidation ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Acyl Coenzyme A ◽  
Long Chain

1. Fluorimetric assays are described for CoASH, acetyl-CoA and long-chain fatty acyl-CoA, and are sensitive to at least 50mumumoles of each. 2. Application of these assays to rat-liver mitochondria oxidizing palmitate in the absence and presence of carnitine indicated two pools of intramitochondrial CoA. One pool could be acylated by palmitate and ATP, and the other pool acylated by palmitate with ATP and carnitine, or by palmitoylcarnitine alone. 3. The intramitochondrial content of acetyl-CoA is increased by the oxidation of palmitate both in the absence and presence of l-malate. 4. The conversion of palmitoyl-CoA into acetyl-CoA by beta-oxidation takes place without detectable accumulation of acyl-CoA intermediates.

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