Browse
Submit Data
Databases
API
Help

Dataset Information

11 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Increased activity of phosphate-dependent glutaminase in liver mitochondria as a result of glucagon treatment of rats.

ABSTRACT: 1. Injection of rats with glucagon leads to an increased effective activity of glutaminase in subsequently isolated liver mitochondria. 2. This effect of glucagon is manifested as a decreased requirement of glutaminase for phosphate in the presence of HCO3-. The HCO3--concentration-dependence is unchanged. 3. The effect of glucagon is lost on disruption of the mitochondria. 4. In accordance with previous reports, incubation of mitochondria in hypo-osmotic media also increases the effective activity of glutaminase. Glucagon increases glutamine hydrolysis at intermediate osmolarities of the suspending medium, but does not affect glutaminase activity when it is already maximally activated by hypo-osmotic conditions. 5. From this and previous work, it seems that hypo-osmotic incubation conditions, EDTA and glucagon may all activate glutaminase by a common mechanism. It is postulated that this mechanism involves modification of the interaction of glutaminase with the mitochondrial inner membrane.

SUBMITTER: Lacey JH

PROVIDER: S-EPMC1162713 | biostudies-other | 1981 Jan

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Localization and some properties of phosphate-dependent glutaminase in disrupted liver mitochondria.

Project description:1. Glutaminase activity in frozen and thawed liver mitochondria was activated by NH4+, phosphate and HCO3-ions and also by ATP . 2. NH4+ and HCO3-ions decreased the requirement of the enzyme for phosphate. The activation by ATP was observed only in the presence of NH4+ or HCO3-ions. 3. In frozen-and-thawed mitochondria, the enzyme was loosely bound to the inner membrane, the Arrhenius plot showing a break at 23 degrees C. On sonication, glutaminase was detached from the membrane and the Arrhenius plot became linear. 4. The apparent Km for glutamine of the membrane-bound form was 6 mM, and that of the soluble form was 21 mM. 5. It is likely that the properties of glutaminase in the intact cell are dependent on the association of this enzyme with the mitochondrial membrane.

| S-EPMC1162368 | biostudies-other

Influence of phospholipids on the activity of phosphate-dependent glutaminase in extracts of rat liver mitochondria.

Project description:Liver glutaminase can be solubilized from frozen-and-thawed mitochondria by treatment with phospholipase A2. Solubilization by this technique markedly changes the kinetic properties of the enzyme. The properties of the membrane-bound form of the enzyme are partially restored by adding phosphatidylcholine or phosphatidylethanolamine to the phospholipase extract. It is concluded that the kinetic properties of liver glutaminase are a function of the interaction of this enzyme with membrane phospholipids.

| S-EPMC1152294 | biostudies-other

Factors influencing the inactivation of phosphate-dependent glutaminase in the matrix fraction of rat liver mitochondria.

Project description:1. The activity of phosphate-dependent glutaminase was measured in a matrix extract of essentially lysosome-free liver mitochondria. 2. ATP, GTP or a non-hydrolysable analogue of ATP stimulated the rapid inactivation of glutaminase, but not of other matrix enzymes. 3. Glutaminase was protected against inactivation if high concentrations of glutamine or low concentrations of NH3 were present. 4. Inactivation of glutaminase in the presence of ATP did not markedly affect the reaction of the enzyme with a specific polyclonal antiserum. 5. These results in a mitochondrial extract are similar to the characteristics of glutaminase inactivation in intact hepatocytes, suggesting a similar mechanism in each case. 6. The presence of a specific ATP-activated protease in the mitochondrial matrix is suggested to be responsible for glutaminase inactivation.

| S-EPMC1149927 | biostudies-other

Purification of phosphate-dependent glutaminase from isolated mitochondria of Ehrlich ascites-tumour cells.

Project description:Phosphate-dependent glutaminase was purified to homogeneity from isolated mitochondria of Ehrlich ascites-tumour cells. The enzyme had an Mr of 135,000 as judged by chromatography on Sephacryl S-300. SDS/polyacrylamide-gel electrophoresis displayed two protein bands, with Mr values of 64,000 and 56,000. Two major immunoreactive peptides of Mr values of 65,000 and 57,000 were found by immunoblot analysis using anti-(rat kidney glutaminase) antibodies. The concentration-dependences for both glutamine and phosphate were sigmoidal, with S0.5 values of 7.6 mM and 48 mM, and Hill coefficients of 1.5 and 1.6, respectively. The glutaminase pH optimum was 9. The activation energy of the enzymic reaction was 58 kJ/mol. The enzyme showed a high specificity towards glutamine. A possible explanation for the different kinetic behaviour found for purified enzyme and for isolated mitochondria [Kovacević (1974) Cancer Res. 34, 3403-3407] should be that a conformational change occurs when the enzyme is extracted from the mitochondrial inner membrane.

| S-EPMC1135344 | biostudies-other

Glucagon and ammonia influence the long-term regulation of phosphate-dependent glutaminase activity in primary cultures of rat hepatocytes.

Project description:1. Glutaminase activity was measured in primary cultures of hepatocytes. 2. Enzyme activity decreased markedly after 24-40 h in culture, and this loss of activity was accompanied by loss of enzyme protein. 3. The loss of activity was delayed by high concentrations of glutamine, and was abolished by the continuous presence of NH4Cl in the culture medium. 4. In cells from rats fed on high-carbohydrate protein-free diet, glutaminase activity was increased by glucagon, but not by dexamethasone. This induction was observed only in the continuous presence of NH3 or high concentrations of glutamine. 5. It is concluded that NH3 and glutamine are essential for the stabilization and induction of glutaminase activity in hepatocytes. The inactivation of glutaminase in hepatocytes and in vivo under certain conditions may be due to lack of NH3 in the extracellular medium.

| S-EPMC1149926 | biostudies-other

Stimulation of the respiratory chain of rat liver mitochondria between cytochrome c1 and cytochrome c by glucagon treatment of rats.

Project description:Mitochondria from glucagon-treated rats oxidize succinate, but not ascorbate plus tetramethylphenylenediamine, faster in the uncoupled state than do control mitochondria. The rate of O(2) uptake in the presence of both substrates is equal to the sum of the rates of the O(2) uptake in the presence of either substrate alone. It is concluded that the mitochondrial respiratory chain is limited at some point between cytochromes b and c and that this step is regulated by glucagon. Measurement of the cytochrome spectra under uncoupled conditions in the presence of succinate and rotenone demonstrates a crossover between cytochromes c and c(1) when control mitochondria are compared with those from glucagon-treated rats, cytochrome c being more oxidized and cytochrome c(1) more reduced in control mitochondria. Under conditions where pyruvate metabolism is studied the control mitochondria are generally more oxidized than those from glucagon-treated rats, the redox state of cytochrome b-566 correlating with the rate of pyruvate metabolism in sucrose medium. However, when the redox state of the mitochondria is taken into account, a crossover between cytochromes c and c(1) is again apparent. The spectra of the b cytochromes are complex, but cytochrome b-562 appears to become more reduced relative to cytochrome b-566 in mitochondria from glucagon-treated rats than in control mitochondria. This can be explained by the existence of a more alkaline matrix in glucagon-treated rats, the redox potential for cytochrome b being pH-sensitive. It is concluded that glucagon stimulates electron flow between cytochromes c(1) and c. The physiological significance of these findings is discussed.

| S-EPMC1185713 | biostudies-other

The maximal activity of phosphate-dependent glutaminase and glutamine metabolism in late-pregnant and peak-lactating rats.

Project description:The maximal activity of phosphate-dependent glutaminase was increased in the small intestine, decreased in the liver and unchanged in the kidney of late-pregnant rats. This was accompanied by increases in the size of both the small intestine and the liver. The maximal activity of phosphate-dependent glutaminase was increased in both the small intestine and liver but unchanged in the kidney of peak-lactating rats. Enterocytes isolated from late-pregnant or peak-lactating rats exhibited an enhanced rate of utilization of glutamine and production of glutamate, alanine and ammonia. Arteriovenous-difference measurements across the gut showed an increase in the net glutamine removed from the circulation in late-pregnant and peak-lactating rats, which was accompanied by enhanced rates of release of glutamate, alanine and ammonia. Arteriovenous-difference measurements for glutamine showed that both renal uptake and skeletal-muscle release of glutamine were not markedly changed during late pregnancy or peak lactation; but pregnant rats showed a hepatic release of the amino acid. It is concluded that, during late pregnancy and peak lactation, the adaptive changes in glutamine metabolism by the small intestine, kidneys and skeletal muscle of hindlimb are similar; however, the liver appears to release glutamine during late pregnancy, but to utilize glutamine during peak lactation.

| S-EPMC1147666 | biostudies-other

Noradrenaline treatment of rats stimulates H2O2 generation in liver mitochondria.

Project description:Treatment of rats with noradrenaline stimulated H2O2 generation in liver mitochondria using succinate, choline or glycerol 1-phosphate as substrate. The dehydrogenase activity with either succinate or choline as substrate showed no change, whereas that with glycerol 1-phosphate increased. The effect was obtained with noradrenaline, but not with dihydroxyphenylserine. Phenoxybenzamine and yohimbine, but not propranolol, prevented the response to noradrenaline treatment. Phenylephrine could stimulate H2O2 generation, whereas isoprenaline had only a marginal effect. Theophylline treatment slightly decreased the generation of H2O2 in liver mitochondria, but treatment with pargyline, Ro4-1284 and dibutyryl cyclic AMP had little effect. These studies showed that noradrenaline might possibly be acting through the alpha 2-adrenergic system.

| S-EPMC1152311 | biostudies-other

Video Education With Result Dependent dIsclosure

Project description:The overall study objective of this trial study is to identify and evaluate strategies to improve the accessibility of the video education with result dependent disclosure (VERDI) model, increasingly utilized as a pre-genetic testing (pretest) education alternative in clinical practice, to better serve a more diverse patient population at risk for hereditary cancers.

| 2403572 | ecrin-mdr-crc

Inhibition by glutamate of phosphate-dependent glutaminase of rat kidney.

Project description:A membrane-associated form of phosphate-dependent glutaminase was derived from sonicated mitochondria and purified essentially free of gamma-glutamyl transpeptidase activity. Increasing concentrations of phosphate cause a sigmoidal activation of the membrane-bound glutaminase. Phosphate also causes a similar effect on the rate of glutaminase inactivation by the two affinity labels, L-2-amino-4-oxo-5-chloropentanoic acid and 6-diazo-5-oxo-L-norleucine, as observed previously for the solubilized and purified enzyme. Therefore the two forms of glutaminase undergo similar phosphate-induced changes in conformation. A sensitive radioactive assay was developed and used to determine the kinetics of glutamate inhibition of the membrane-associated glutaminase. The Km for glutamine decreases from 36 to 4 mM when the phosphate concentration is increased from 5 to 100 mM. Glutamate is a competitive inhibitor with respect to glutamine at both high and low concentrations of phosphate. However, the Ki for glutamate is increased from 5 to 52 mM with increasing phosphate concentration. Therefore glutamine and glutamate interact with the same site on the glutaminase, but the specificity of the site is determined by the available phosphate concentration.

| S-EPMC1153898 | biostudies-other

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data