6-Phosphofructo-2-kinase and control of cryoprotectant synthesis in freeze tolerant frogs

Illanes, María Dolores Vázquez; Storey, Kenneth B.

doi:10.1016/0304-4165(93)90092-m

Cited by 20 publications

(13 citation statements)

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“…The regulation of the bifunctional enzyme activity by gene expression and phosphorylation/dephosphorylation at serine is best described in the mammalian liver where the concentration of F-2,6-P 2 is determined by the amount of the enzyme and phosphorylation state. This may be due to a lack of specific hormones in the species, or as is the case in freeze tolerant frogs and turtles, the hormonal signals are precluded because of insufficient blood flow in the frozen state [107]. The situation is similar in the other species and tissue specific isoforms of the bifunctional enzyme, although the metabolic signal varies.…”

Section: The Enzymes That Synthesize and Degrade F-26-pmentioning

confidence: 99%

“…Some species of wood frogs (Rana sylvatica) and turtles (Chrysemys picta marginata), can survive a prolonged time with up to 50% of the body water as ice [90,107]. Some species of wood frogs (Rana sylvatica) and turtles (Chrysemys picta marginata), can survive a prolonged time with up to 50% of the body water as ice [90,107].…”

Section: Adaptive Survival Strategiesmentioning

confidence: 99%

“…These animals use glucose, as well as other compounds, as a cryoprotectant to keep the core organs from being damaged by ice crystal formation [90,107]. Furthermore, the skeletal muscle is ischemic due to the lack of bloodflow in the frozen state and the increased F-2,6-P 2 aids in the switch from aerobic to anaerobic metabolism in the muscle [107]. Clearly, to establish such a high level of glucose the other routes of G6P utilization in the liver must be tightly controlled.…”

Section: Adaptive Survival Strategiesmentioning

confidence: 99%

“…Some species do not utilize hormonal controls at all. This may be due to a lack of specific hormones in the species, or as is the case in freeze tolerant frogs and turtles, the hormonal signals are precluded because of insufficient blood flow in the frozen state [107]. Characterization of the mechanisms of protein post-translational modifications used by these species is an active area of biochemical research.…”

Section: The Enzymes That Synthesize and Degrade F-26-pmentioning

confidence: 99%

“…Some species of wood frogs (Rana sylvatica) and turtles (Chrysemys picta marginata), can survive a prolonged time with up to 50% of the body water as ice [90,107]. These animals use glucose, as well as other compounds, as a cryoprotectant to keep the core organs from being damaged by ice crystal formation [90,107]. The intracellular concentration of glucose can be as high as 300 mM and this glucose is derived from hepatic glycogenolysis and subsequent export to the other tissues.…”

Section: Adaptive Survival Strategiesmentioning

confidence: 99%

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Fructose‐2,6‐bisphosphate and control of carbohydrate metabolism in eukaryotes

1999

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Fructose-2,6-bisphosphate is an important intracellular biofactor in the control of carbohydrate metabolic fluxes in eukaryotes. It is generated from ATP and fructose-6-phosphate by 6-phosphofructo-2-kinase and degraded to fructose-6-phosphate and phosphate ion by fructose-2,6-bisphosphatase. In most organisms these enzymatic activities are contained in a single polypeptide. The reciprocal modulation of the kinase and bisphosphatase activities by post-translational modifications places the level of the biofactor under the control of extra-cellular signals. In general, these signals are generated in response to changing nutritional states, therefore, fructose-2,6-bisphosphate plays a role in the adaptation of organisms, and the tissues within them, to changes in environmental and metabolic states. Although the specific mechanism of fructose-2,6-bisphosphate action varies between species and between tissues, most involve the allosteric activation of 6-phosphofructo-1-kinase and inhibition of fructose-1,6-bisphosphatase. These highly conserved enzymes regulate the fructose-6-phosphate/fructose-1,6-bisphosphate cycle, and thereby, determine the carbon flux. It is by reciprocal modulation of these activities that fructose-2,6-bisphosphate plays a fundamental role in eukaryotic carbohydrate metabolism.

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Section: The Enzymes That Synthesize and Degrade F-26-pmentioning

confidence: 99%