The Pathway of Glutamate Oxidation in Rabbit Reticulocytes

J, Rost; Rapoport, S.

doi:10.1111/j.1432-1033.1972.tb01745.x

Cited by 4 publications

(3 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Oxaloacetate itself is a good substrate of both intact reticulocytes [14] and their isolated mitochondria [15]. From experiments with [U-14C]glutamine as predominant respiratory substrate it has been postulated [4] that the carbon skeleton of glutamate furnishes acetyl-CoA via oxaloacetate and pyruvate. Thus oxaloacetate and amino acids which form it are sources of acetyl-CoA competitive with the fatty acids.…”

Section: Discussionmentioning

confidence: 99%

The Oxidation of Fatty Acids by Rabbit Reticulocytes and Their Isolated Mitochondria

Schultze

Augustin

et al. 1972

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

The oxidation of fatty acids by rabbit reticulocytes and their isolated mitochondria has been studied with [1‐14C]octanoate, [U‐14C]palmitate and [U‐14C]oleate.The fatty acids, particularly octanoate, represent good respiratory substrates.They are activated both by carnitine‐dependent and carnitine‐independent systems, the former predominating for palmitate, the latter for octanoate.The oxidation of palmitate presents a nearly hyperbolic substrate‐saturation curve. The limitation lies presumably in the capacity of the activating enzymes for the long‐chain fatty acids on in their translocation through the mitochondrial membrane. With octanoate no indication of saturation was observed. It may contribute as much as 65% of the respiratory substrate. Oxaloacetate exerts a double effect on the oxidation of fatty acids. In low concentrations it activates their oxidation as an acceptor for acetyl‐CoA; in high concentrations it serves itself as a source of acetyl‐CoA and produces a competitive inhibition. It is estimated that fatty acids furnish about 10% of the respiratory substrate of reticulocytes under physiological conditions.

show abstract

Section: Discussionmentioning

confidence: 99%

The Oxidation of Fatty Acids by Rabbit Reticulocytes and Their Isolated Mitochondria

Schultze

Augustin

et al. 1972

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

show abstract

“…In a previous communication it was concluded that in reticulocytes oxaloacetate which arises from amino acids, in particular glutamate and aspartate, may also be the source of pyruvate and acetyl-CoA [1 ]. The evidence was indirect; it consisted in dilution experiments, which showed a diminution of 14 CO2 formation from variously labelled 14 C pyruvate from ~4C acetate, as well as 14 C-labelled fatty acids by glutamine and oxaloacetate.…”

Section: Introductionmentioning

confidence: 99%

On the formation of acetyl‐CoA from glutamine and the mutual interconversion between oxaloacetate and pyruvate in rabbit reticulocytes

Müller

Rapoport

1974

FEBS Letters

View full text Add to dashboard Cite

“…The third pool consists of the components of the citrate cycle, in particular citrate, and of the amino acids which are closely related to the citrate cycle, such as glutamate and aspartate [38].…”

Section: Meiaholic Pathwaysmentioning

confidence: 99%

Quantification of Pathways of Glucose Utilization and Balance of Energy Metabolism of Rabbit Reticulocytes

Siems

Müller

Dumdey

et al. 1982

European Journal of Biochemistry

View full text Add to dashboard Cite

In this work it is demonstrated that glucose constitutes the main substrate of energy metabolism of rabbit reticulocytes under aerobic conditions in the presence of 5 mM glucose. Amino acids and fatty acids are minor sources of energy. The shares of processes utilizing glucose in reticulocytes were estimated from tracer experiments. A new mathematical technique used permits the derivation of closed terms for the specific radioactivity of single positions of C atoms of the metabolites of the citrate cycle. By means of regression analysis, the undetermined flux rates in the citrate cycle were calculated.On the basis of the data an overall balance sheet of glucose utilization and of ATP generation is given. About 45 of the glucose of reticulocytes is catabolized via the citrate cycle, about the same percentage yields lactate. Only 2 of the glucose was oxidized in the oxidative pentose pathway whereas the remainder is used for the formation of serine and glycine required for hemoglobin synthesis.These results are related to knowledge about the main processes utilizing ATP in reticulocytes, i.e. the synthesis of hemoglobin and the energy-dependent proteolysis. Our approach to the investigation of metabolic relations in the reticulocytes can be applied to other tissues in which equilibria between large metabolite pools play a roleThe quantitative assessment of metabolic pathways in cells poses considerable difficulties. A clear-cut balance so far is only available for the simplest cell, the mature erythrocyte with its rudimentary metabolism [l]. It consumes only glucose which is utilized to about 90% by glycolysis and about 10% by the oxidative pentose pathway. In other cells several substrates are utilized both by anaerobic and aerobic pathways. Furthermore there are a multitude of synthetic processes. The complexities are compounded by compartmentation. Our knowledge about the distribution of energy production and utilization is also unsatisfactory for any type of cell. Even for the mature red cell there is no answer as yet concerning the apportionment of ATP-consuming processes, mostly located in the cell membrane [2], even though a good understanding exists with respect to the amount and regulation of ATP production [3 -51. Generally isotopic methods with 14C-labeled substrates have been used for the assessment of metabolic pathways. They involve a number of problems, such as isotopic exchange which may simulate metabolic flux, the occurrence of large pools of metabolites and, of course, compartmentation. The uneven distribution of the radioactivity among different C atoms of a metabolic is a further complication.For estimation of the distribution of glucose between the oxidative pentose and Embden-Meyerhof pathways the ratio between the radioactivities of the COz derived from [1-14C]-glucose and [6-14C]glucose has often been used. The calculation is based on the consideration that in the former pathway COZ is formed only from the C-I atom of glucose, whereas it is derived from both C-1 and C-6 atoms in the Embden...

show abstract

The Pathway of Glutamate Oxidation in Rabbit Reticulocytes

Cited by 4 publications

References 12 publications

The Oxidation of Fatty Acids by Rabbit Reticulocytes and Their Isolated Mitochondria

The Oxidation of Fatty Acids by Rabbit Reticulocytes and Their Isolated Mitochondria

On the formation of acetyl‐CoA from glutamine and the mutual interconversion between oxaloacetate and pyruvate in rabbit reticulocytes

Quantification of Pathways of Glucose Utilization and Balance of Energy Metabolism of Rabbit Reticulocytes

Contact Info

Product

Resources

About