Glycolysis is operative in amphibian oocytes

Guixé, Victoria; Preller, Ana; Kessi, Eduardo; Hofer, Hans Werner; Ureta, Tito

doi:10.1016/0014-5793(94)80559-8

Cited by 6 publications

(6 citation statements)

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“…Separation and identification of metabolic intermediates was as described in [3], except that the CarboPac PA1 column was equilibrated with 90 % solution A (100 mM NaOH) and 10 % solution B (1 M sodium acetate\100 mM NaOH) and eluted at a flow rate of 0.5 ml\min with the following gradient : T ! l 10 % ; T #!…”

Section: Separation Of Metabolic Intermediates By Ion-exchange Chromamentioning

confidence: 99%

“…Labelled glucose (microinjected or present in the incubation medium) is readily incorporated into glycogen and, to a minor extent, released as CO # through the pentose phosphate pathway only, since [6-"%C]glucose does not produce "%CO # [1,2]. All enzymes of glucose utilization are present in oocyte homogenates [1], including phosphofructokinase [3] and fructose-1,6bisphosphatase [4], previously thought to be absent from these cells [5]. A recent paper from our laboratory [3] reported that a significant amount of carbon from [U-"%C]glucose was found, after 5 min incubation, in lactate.…”

Section: Introductionmentioning

confidence: 99%

“…All enzymes of glucose utilization are present in oocyte homogenates [1], including phosphofructokinase [3] and fructose-1,6bisphosphatase [4], previously thought to be absent from these cells [5]. A recent paper from our laboratory [3] reported that a significant amount of carbon from [U-"%C]glucose was found, after 5 min incubation, in lactate. It was also shown that labelled ATP was formed, after 1 min, from microinjected fructose 6-[$#P]phosphate.…”

Section: Introductionmentioning

confidence: 99%

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Glycogen synthesis in amphibian oocytes: evidence for an indirect pathway

Kessi

Guixé

Preller

et al. 1996

Biochemical Journal

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Glycogen is the main end product of glucose metabolism in amphibian oocytes. However, in the first few minutes after [U-14C]glucose microinjection most of the label is found in lactate. The burst of lactate production and the shape of the time curves for the labelling of glucose 6-phosphate, fructose 6-phosphate, glucose 1-phosphate and glycogen suggest a precursor-product relationship of lactate with respect to glycogen and its intermediates. Expansion (by microinjection) of the pool of glycolytic intermediates, such as dihydroxyacetone phosphate, glyceraldehyde 3-phosphate, 3-phosphoglycerate or phosphoenolpyruvate, results in a marked decrease in [U-14C]glucose incorporation into glycogen. After co-injection of doubly labelled glucoses, extensive detritiation (93%) of the glucosyl units of glycogen was observed with [2-3H, U-14C]glucose and partial detritiation with [3-3H,U-14C]glucose (34%) or [5-3H,U-14C]glucose (46%). After injection of [6-3H,U-14C]glucose, a small but significant and reproducible detritiation (13%) in glycogen was observed. Co-injection of [U-14C]glucose and 3-mercaptopicolinate resulted in marked inhibition of glycogen labelling. Half-maximal inhibition was observed at 0.58 mM 3-mercaptopicolinate, which agrees with the IC50 value (0.47 mM) for the inhibition in vitro of phosphoenolpyruvate carboxykinase activity. We concluded that in frog oocytes most of the glucosyl units are incorporated into glycogen by an indirect pathway involving breakdown of glucose to lactate, which is then converted into glycogen via gluconeogenesis. Both processes, glycolytic degradation of glucose to lactate and subsequent reconversion of the latter into hexose phosphates and glycogen, occur in the same cell.

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Section: Separation Of Metabolic Intermediates By Ion-exchange Chromamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Glycogen synthesis in amphibian oocytes: evidence for an indirect pathway

Kessi

Guixé

Preller

et al. 1996

Biochemical Journal

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“…Glycolysis is operative in grown amphibian oocytes [1], although glucose injected into the cells is mostly utilized for glycogen synthesis [2, 3]. Glucose incorporation into the polysaccharide occurs preferentially by the so called indirect pathway, which involves prior degradation of glucose into three carbon compounds which then by gluconeogenesis, regenerate hexoses‐P and UDP‐glucose, the proximate glycogen precursor [4].…”

Section: Introductionmentioning

confidence: 99%

In vivo operation of the pentose phosphate pathway in frog oocytes is limited by NADP⁺ availability

Preller¹,

Guixé²,

Ureta³

1999

FEBS Letters

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Evolution of CO P from labelled glucose microinjected into frog oocytes in vivo may be ascribed to the pentose-P pathway, as measured by radioactive CO P production from [1-IR C] and [6-IR C]glucose. Coinjection of NADP + and [ IR C]glucose significantly stimulated IR CO P production. The effect depends on the amount of NADP + injected, half maximal stimulation being obtained at 0.13 mM. The increase in CO P production was also observed with microinjected glucose-1-P, glucose-6-P or fructose-6-P used as substrates.

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“…1, left). Glycolytic intermediates cannot be detected at those early times, i.e., glucose breakdown proceeds at a very low steady-state of intermediates (7), a fact that suggests channelling of the pathway. Then, labeled glycogen begins to accumulate and hexoses-P can be detected.…”

Section: Two Pathways For Glycogen Synthesis In Frog Oocytesmentioning

confidence: 99%

Frog Oocytes: A Living Test Tube for Studies on Metabolic Regulation

Ureta

Preller²,

Kessi³

2001

IUBMB Life

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This review is intended to illustrate how live frog oocytes may be advantageously used to address the study of some problems of in vivo glucose metabolism. Glucose microinjected into the cells is preferentially committed to glycogen synthesis. We present evidence showing that both the direct and indirect pathways for polysaccharide deposition are operative in oocytes. A small amount of the injected glucose (<5%) is released as labeled CO2 mainly through the pentose-P pathway. Coinjection of NADP+ and glucose significantly stimulates 14CO2 production, half-maximal stimulation being obtained at 0.13 mM. Finally, we show the use of frog oocytes to measure in vivo the control coefficient of hexokinase on glycogen synthesis and the pentose-P pathway. A value of 0.7 was found for the control coefficient of hexokinase on glycogen synthesis, while the enzyme has no control at all over the pentose-P pathway. Therefore, the frog oocyte may be used as a living test tube for the study of almost any metabolic process of interest.

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Glycolysis is operative in amphibian oocytes

Cited by 6 publications

References 8 publications

Glycogen synthesis in amphibian oocytes: evidence for an indirect pathway

Glycogen synthesis in amphibian oocytes: evidence for an indirect pathway

In vivo operation of the pentose phosphate pathway in frog oocytes is limited by NADP⁺ availability

Frog Oocytes: A Living Test Tube for Studies on Metabolic Regulation

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Glycolysis is operative in amphibian oocytes

Cited by 6 publications

References 8 publications

Glycogen synthesis in amphibian oocytes: evidence for an indirect pathway

Glycogen synthesis in amphibian oocytes: evidence for an indirect pathway

In vivo operation of the pentose phosphate pathway in frog oocytes is limited by NADP+ availability

Frog Oocytes: A Living Test Tube for Studies on Metabolic Regulation

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In vivo operation of the pentose phosphate pathway in frog oocytes is limited by NADP⁺ availability