scholarly journals The activities and intracellular distribution of nicotinamide-adenine dinucleotide phosphate-malate dehydrogenase, phosphoenolpyruvate carboxykinase and pyruvate carboxylase in rat, guinea-pig and rabbit tissues

1975 ◽  
Vol 146 (2) ◽  
pp. 329-332 ◽  
Author(s):  
D E Saggerson ◽  
C J Evans
Keyword(s):  
Adipose Tissue ◽  
Guinea Pig ◽  
Malate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Intracellular Distribution ◽  
Kidney Cortex ◽  
Carboxylase Activity ◽  
Liver And Kidney

1. Measurements are presented of the activity and intracellular distribution of phosphoenolypruvate carboxykinase, pyruvate carboxylase and NADP-malate dehydrogenase in rat, guinea-pig and rabbit liver and kidney cortex, together with previously obtained measurements of these enzymes in adipose tissue. 2. In all three tissues pyruvate carboxylase activity was greatest in the rat and lowest in the rabbit. 3. Guinea pig and rabbit were very similar to each other with respect to the extramitochondrial-mitochondrial distribution of phosphoenolpyruvate carboxykinase in all three tissues. 4. NADP-malate dehydrogenase was present in all three tissues in the rat, present in kidney cortex and adipose tissue in the guinea pig and absent from all tissues examines in the rabbit.

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.

scholarly journals Glutamine synthesis from aspartate in guinea-pig renal cortex

1990 ◽  
Vol 268 (2) ◽  
pp. 437-442 ◽  
Author(s):  
G Baverel ◽  
G Martin ◽  
C Michoudet
Keyword(s):  
Glutamine Synthetase ◽  
Guinea Pig ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Tricarboxylic Acid Cycle ◽  
Kidney Cortex ◽  
Carbon And Nitrogen ◽  
Ammonia Release ◽  
Glutamine Synthesis ◽  
Methionine Sulphoximine ◽  
Main Carbon

1. Glutamine was found to be the main carbon and nitrogen product of the metabolism of aspartate in isolated guinea-pig kidney-cortex tubules. Glutamate, ammonia and alanine were only minor products. 2. Carbon-balance calculations and the release of 14CO2 from [U-14C]aspartate indicate that oxidation of the aspartate carbon skeleton occurred. 3. A pathway involving aspartate aminotransferase, glutamate dehydrogenase, glutamine synthetase, phosphoenolpyruvate carboxykinase, pyruvate kinase, pyruvate dehydrogenase and enzymes of the tricarboxylic acid cycle is proposed for the conversion of aspartate into glutamine. 4. Evidence for this pathway was obtained by: (i) inhibiting aspartate removal by amino-oxyacetate, an inhibitor of transaminases, (ii) the use of methionine sulphoximine, an inhibitor of glutamine synthetase, which induced a large increase in ammonia release from aspartate, (iii) the use of quinolinate, an inhibitor of phosphoenolpyruvate carboxykinase, which inhibited glutamine synthesis from aspartate, (iv) the use of alpha-cyano-4-hydroxycinnamate, an inhibitor of the mitochondrial transport of pyruvate, which caused an accumulation of pyruvate from aspartate, and (v) the use of fluoroacetate, an inhibitor of aconitase, which inhibited glutamine synthesis with concomitant accumulation of citrate from aspartate.

Osmotic regulation in isolated liver and kidney slices

1960 ◽  
Vol 199 (6) ◽  
pp. 1227-1231 ◽  
Author(s):  
A. G. Swan ◽  
A. T. Miller
Keyword(s):  
Guinea Pig ◽  
Osmotic Pressure ◽  
Kidney Cortex ◽  
Osmotic Regulation ◽  
Sodium Potassium ◽  
Pig Liver ◽  
Kidney Slices ◽  
Liver And Kidney ◽  
Isolated Liver ◽  
Guinea Pig Liver

Slices of guinea pig liver and kidney cortex were incubated under a variety of metabolic and osmotic conditions and the changes in tissue osmotic pressure and in water and electrolyte distribution were measured. The fresh tissues were approximately isotonic with serum, so that swelling was not due to initially hypertonic cell contents. Autolysis was not an important cause of swelling, probably because of leakage of the autolytic products from the cells. Influx of NaCl was sufficient to account for passage of water into the cells. Based on measured fluxes of sodium, potassium and chloride alone, the water of swelling was isotonic or hypertonic but never hypotonic.

scholarly journals The activity of phosphoenolpyruvate carboxykinase in rat tissues. Assay techniques and effects of dietary and hormonal changes

1975 ◽  
Vol 152 (2) ◽  
pp. 401-408 ◽  
Author(s):  
Christopher I. Pogson ◽  
Stephen A. Smith
Keyword(s):  
Adipose Tissue ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Alloxan Diabetes ◽  
Forward Direction ◽  
Epididymal Adipose Tissue ◽  
Rat Tissues ◽  
Hormonal Changes ◽  
Mitochondrial Enzyme ◽  
Forward Reaction ◽  
Liver And Kidney

1. Phosphoenolpyruvate carboxykinase was assayed by three methods: (i) incorporation of H14CO3- into oxaloacetate: (ii) conversion of oxaloacetate into phosphoenolpyruvate, subsequently assayed enzymically; and (iii) transfer of 32P from [γ-32P]GTP to oxaloacetate. 2. Enzyme activity is increased in liver and epididymal adipose tissue in alloxan-diabetes and starvation, and in kidney in starved, acidotic and steroid-treated animals. 3. The ratios of the ‘back’ to the ‘forward’ reactions in liver, kidney and epididymal adipose tissue are different and characteristic of each tissue; they differ markedly from values reported for the purified mitochondrial enzyme. 4. The ratio of the ‘back’ to ‘forward’ reaction in any one tissue is constant in adrenalectomized, diabetic, acidotic and steroid-treated animals. 5. In starved animals, the ratio is increased in liver and kidney, but decreased in epididymal adipose tissue. 6. Administration of l-tryptophan results in an acute (1h) increase in activity measured in the ‘forward’ direction alone in liver and epididymal adipose tissue, but not in kidney.

scholarly journals Metabolic changes associated with the occurrence of fatty liver and kidney syndrome in chicks

1978 ◽  
Vol 40 (2) ◽  
pp. 221-234 ◽  
Author(s):  
C. C. Whitehead ◽  
D. W Bannister ◽  
Maureen E. Cleland
Keyword(s):  
Lactate Dehydrogenase ◽  
Fatty Liver ◽  
Pyruvate Carboxylase ◽  
Liver Weight ◽  
High Plasma ◽  
Broiler Chicks ◽  
Plasma Lactate ◽  
Carboxylase Activity ◽  
Lactate Dehydrogenase Activity ◽  
Liver And Kidney

1. The changes in a number of metabolic measurements brought about by low-biotin diets associated with high and low incidences of fatty liver and kidney syndrome (FLKS) were studied in healthy 4-week-old broiler chicks.2. Liver pyruvate carboxylase (pyruvate: CO2 ligase (ADP); EC 6.4.1.1) activity was low in birds fed on a diet causing a high incidence of FLKS but the addition of fat or protein to this diet, to decrease the incidence of FLKS, increased enzyme activity.3. Liver weights, blood lactate concentrations, plasma lactate dehydrogenase (l-lactate:NAD oxidoreductase; EC 1.1.1.27) activities and values for C16:1:C18:0 fatty acid in liver, adipose tissue and plasma triglyceride were highest in birds fed on the high-FLKS diet and all measurements were negatively correlated with pyruvate carboxylase activity.4. Birds with high plasma lactate dehydrogenase activity or triglyceride C16:1:C18:0 values were the most likely to develop FLKS when fasted.5. There was no evidence that increased liver weight was associated with increased activities of certain other liver enzymes.6. It is concluded that FLKS occurs in birds with little or no hepatic gluconeogenic capacity via pyruvate carboxylase as a result of a dietary insufficiency of biotin but that the initiation of the syndrome is probably associated with the inhibition of other pathways of gluconeogenesis.

scholarly journals Stimulation by glucose of gluconeogenesis in hepatocytes isolated from starved rats

1987 ◽  
Vol 245 (3) ◽  
pp. 661-668 ◽  
Author(s):  
M Rigoulet ◽  
X M Leverve ◽  
P J A M Plomp ◽  
A J Meijer
Keyword(s):  
Steady State ◽  
Production Rate ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Production ◽  
Carboxylase Activity ◽  
Maximal Stimulation ◽  
Intracellular Concentrations ◽  
Effect Of Glucose ◽  
Stimulation Of

Control properties of the gluconeogenic pathway in hepatocytes isolated from starved rats were studied in the presence of glucose. The following observations were made. (1) Glucose stimulated the rate of glucose production from 20 mM-glycerol, from a mixture of 20 mM-lactate and 2 mM-pyruvate, or from pyruvate alone; no stimulation was observed with 20 mM-alanine or 20 mM-dihydroxyacetone. Maximal stimulation was obtained between 2 and 5 mM-glucose, depending on the conditions. At concentrations above 6 mM, gluconeogenesis declined again, so that at 10 mM-glucose the glucose production rate became equal to that in its absence. (2) With glycerol, stimulation of gluconeogenesis by glucose was accompanied by oxidation of cytosolic NADH and reduction of mitochondrial NAD+ and was insensitive to the transaminase inhibitor amino-oxyacetate; this indicated that glucose accelerated the rate of transport of cytosolic reducing equivalents to the mitochondria via the glycerol 1-phosphate shuttle. (3) With lactate plus pyruvate (10:1) as substrates, stimulation of gluconeogenesis by glucose was almost additive to that obtained with glucagon. From an analysis of the effect of glucose on the curves relating gluconeogenic flux and the steady-state intracellular concentrations of gluconeogenic intermediates under various conditions, in the absence and presence of glucagon, it was concluded that addition of glucose stimulated both phosphoenolpyruvate carboxykinase and pyruvate carboxylase activity.

DDT-Induced Stimulation of Key Gluconeogenic Enzymes In Rat Kidney Cortex

1972 ◽  
Vol 50 (2) ◽  
pp. 225-229 ◽  
Author(s):  
S. Kacew ◽  
R. L. Singhal ◽  
G. M. Ling
Keyword(s):  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Glucocorticoid Hormones ◽  
Rat Kidney Cortex ◽  
Gluconeogenic Enzymes ◽  
Maximal Stimulation ◽  
Adrenalectomized Rats ◽  
Stimulation Of

Administration of technical DDT or o,p′-DDT produced marked increases in pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1,6-diphosphatase, and glueose-6-phospfaatase activities in rat kidney cortex. Significant increases in these key gluconeogenic enzymes occurred at 2–3 days and maximal stimulation was seen 5–7 days after the beginning of o,p′-DDT treatment. This DDT isomer, when given to adrenalectomized rats, produced increases in renal enzymes similar to those observed in intact animals. Furthermore, since administration of triamcinolone to o,p′-DDT-treated rats failed to potentiate the action of this insecticide on various enzymes, evidence indicates that the stimulation of kidney cortex gluconeogenesis by DDT is not mediated through a release of glucocorticoid hormones from the adrenal cortex.

ENZYMES OF PYRUVATE AND PHOSPHOENOLPYRUVATE CARBOXYLATION IN RUMEN BACTERIA

1974 ◽  
Vol 54 (4) ◽  
pp. 595-603 ◽  
Author(s):  
A. S. ATWAL ◽  
F. D. SAUER
Keyword(s):  
Calcium Phosphate ◽  
Ammonium Sulphate ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Rumen Fluid ◽  
Maximum Activity ◽  
Rumen Bacteria ◽  
Carboxylase Activity ◽  
Mixed Bacteria ◽  
Pep Carboxykinase

Extracts of mixed bacteria collected from bovine rumen fluid contained enzymes that carboxylated pyruvate and phosphoenolpyruvate (PEP). Fresh extracts showed high pyruvate carboxylase activity (EC 6.4.1.1. pyruvate carboxylase) which, however, was cold-labile and lost activity on dialysis at 4 C. Enzyme(s) catalyzing the carboxylation of PEP were stable under these conditions. The carboxylation of PEP was maximally stimulated by ADP and to a lesser degree by GDP. The ADP–requiring PEP carboxykinase [EC 4.1.1.49 phosphoenolpyruvate carboxykinase (ATP)] was equally active with either Mg++ or Mn++ and showed maximum activity at pH 6.5. The GDP–requiring PEP carboxykinase [EC 4.1.1.32 phosphoenolpyruvate carboxykinase (GTP)] required Mn++ and was almost inactive if Mg++ was substituted. Maximum activity was at pH 7.0. These nucleotides were most effective at 2.5-mM concentration and were inhibitory at higher concentrations. In the absence of added ADP or GDP, the carboxylation of PEP continued at a low but persistent rate. Precipitation with ammonium sulphate and adsorption on calcium phosphate gel resulted in fractions containing different proportions of the three activities. These results suggest that in mixed rumen bacterial extracts there are four separate enzymes capable of synthesizing oxaloacetate: one that catalyzes the carboxylation of pyruvate and three that catalyze the carboxylation of PEP.

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