Mitochondrial Oxidative Phosphorylation Is Regulated by Fructose 1,6-Bisphosphate

In numerous cell types, tumoral cells, proliferating cells, bacteria, and yeast, respiration is inhibited when high concentrations of glucose are added to the culture medium. This phenomenon has been named the “Crabtree effect.” We used yeast to investigate (i) the short term event(s) associated with the Crabtree effect and (ii) a putative role of hexose phosphates in the inhibition of respiration. Indeed, yeast divide into “Crabtree-positive,” where the Crabtree effect occurs, and “Crabtree-negative,” where it does not. In mitochondria isolated from these two categories of yeast, we found that low, physiological concentrations of glucose 6-phosphate and fructose 6-phosphate slightly (20%) stimulated the respiratory flux and that this effect was strongly antagonized by fructose 1,6-bisphosphate (F16bP). On the other hand, F16bP by itself was able to inhibit mitochondrial respiration only in mitochondria isolated from a Crabtree-positive strain. Using permeabilized spheroplasts from Crabtree-positive yeast, we have shown that the sole effect observed at physiological concentrations of hexose phosphates is an inhibition of oxidative phosphorylation by F16bP. This F16bP-mediated inhibition was also observed in isolated rat liver mitochondria, extending this process to mammalian cells. From these results and taking into account that F16bP is able to accumulate in the cell cytoplasm, we propose that F16bP regulates oxidative phosphorylation and thus participates in the establishment of the Crabtree effect. In numerous cell types, tumoral cells, proliferating cells, bacteria, and yeast, respiration is inhibited when high concentrations of glucose are added to the culture medium. This phenomenon has been named the “Crabtree effect.” We used yeast to investigate (i) the short term event(s) associated with the Crabtree effect and (ii) a putative role of hexose phosphates in the inhibition of respiration. Indeed, yeast divide into “Crabtree-positive,” where the Crabtree effect occurs, and “Crabtree-negative,” where it does not. In mitochondria isolated from these two categories of yeast, we found that low, physiological concentrations of glucose 6-phosphate and fructose 6-phosphate slightly (20%) stimulated the respiratory flux and that this effect was strongly antagonized by fructose 1,6-bisphosphate (F16bP). On the other hand, F16bP by itself was able to inhibit mitochondrial respiration only in mitochondria isolated from a Crabtree-positive strain. Using permeabilized spheroplasts from Crabtree-positive yeast, we have shown that the sole effect observed at physiological concentrations of hexose phosphates is an inhibition of oxidative phosphorylation by F16bP. This F16bP-mediated inhibition was also observed in isolated rat liver mitochondria, extending this process to mammalian cells. From these results and taking into account that F16bP is able to accumulate in the cell cytoplasm, we propose that F16bP regulates oxidative phosphorylation and thus participates in the establishment of the Crabtree effect. In aerobic organisms, glycolysis and oxidative phosphorylation are coordinated to fulfill the cell energy demand. In some conditions, such as glucose addition to the cells, one can observe an increase in glycolytic flux, whereas respiration is inhibited. This has been observed in tumoral cells (1.Crabtree H.G. Biochem. J. 1929; 22: 1289-1298Crossref Google Scholar), nontumoral proliferating cells (2.Greiner E.F. Guppy M. Brand K. J. Biol. Chem. 1994; 269: 31484-31490Abstract Full Text PDF PubMed Google Scholar), some bacteria (3.Mustea I. Muresian T. Cancer. 1967; 20: 1499-1501Crossref PubMed Scopus (12) Google Scholar), and some yeast species (4.Van Urk H. Voll W.S. Scheffers W.A. Van Dijken J.P. Appl. Environ. Microbiol. 1990; 56: 281-287Crossref PubMed Google Scholar). In all of these cases, glucose induces a transition to a mostly fermentative metabolism. This phenomenon has been named the “Crabtree effect,” after its discoverer (1.Crabtree H.G. Biochem. J. 1929; 22: 1289-1298Crossref Google Scholar). The physiological events that could clearly explain the occurrence of the Crabtree effect are currently unknown, although many hypotheses have been laid (4.Van Urk H. Voll W.S. Scheffers W.A. Van Dijken J.P. Appl. Environ. Microbiol. 1990; 56: 281-287Crossref PubMed Google Scholar, 5.Gatt S. Racker E. J. Biol. Chem. 1959; 234: 1015-1023Abstract Full Text PDF PubMed Google Scholar, 6.Chapman C. Bartley W. Biochem. J. 1969; 111: 609-613Crossref PubMed Scopus (15) Google Scholar, 7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar). It has been proposed, for instance, that it could originate from a competition between mitochondria and glycolytic enzymes for free ADP and inorganic phosphate (5.Gatt S. Racker E. J. Biol. Chem. 1959; 234: 1015-1023Abstract Full Text PDF PubMed Google Scholar, 8.Sanchez N.S. Calahorra M. González-Hernandez J.C. Peña A. Yeast. 2006; 23: 361-374Crossref PubMed Scopus (29) Google Scholar). Indeed, the respiration of isolated mitochondria is decreased in the presence of ADP-consuming systems, such as reconstituted glycolysis or the phosphocreatine/creatine kinase system (5.Gatt S. Racker E. J. Biol. Chem. 1959; 234: 1015-1023Abstract Full Text PDF PubMed Google Scholar). Nevertheless, after glucose addition, ADP levels remain constant or even increase in yeast (6.Chapman C. Bartley W. Biochem. J. 1969; 111: 609-613Crossref PubMed Scopus (15) Google Scholar, 9.Beauvoit B. Rigoulet M. Bunoust O. Raffard G. Canioni P. Guerin B. Eur. J. Biochem. 1993; 214: 163-172Crossref PubMed Scopus (45) Google Scholar) and hepatoma cells (7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar). Furthermore, in both models, there is a transient decrease in cytoplasmic Pi levels (7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar, 10.den Hollander J.A. Ugurbil K. Brown T.R. Shulman R.G. Biochemistry. 1981; 20: 5871-5880Crossref PubMed Scopus (176) Google Scholar), pointing to a possible role of Pi or phosphate potential (ΔGp) in this process. It has been proposed that one of the short term events leading to the Crabtree effect is an overflow through pyruvate decarboxylase, since it has been observed that in Crabtree-positive yeast strains, its activity increases after a glucose pulse (4.Van Urk H. Voll W.S. Scheffers W.A. Van Dijken J.P. Appl. Environ. Microbiol. 1990; 56: 281-287Crossref PubMed Google Scholar). Nonetheless, pyruvate decarboxylase seems to be an important bypass of pyruvate dehydrogenase during oxidative metabolism (11.Boubekeur S. Bunoust O. Camougrand N. Castroviejo M. Rigoulet M. Guerin B. J. Biol. Chem. 1999; 274: 21044-21048Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar). It was also proposed that changes in mitochondrial outer membrane permeability could be critical for the regulation of the Crabtree effect (12.Zizi M. Forte M. Blachly-Dyson E. Colombini M. J. Biol. Chem. 1994; 269: 1614-1616Abstract Full Text PDF PubMed Google Scholar, 13.Lee A.C. Zizi M. Colombini M. J. Biol. Chem. 1994; 269: 30974-30980Abstract Full Text PDF PubMed Google Scholar). From results obtained with reconstituted systems (12.Zizi M. Forte M. Blachly-Dyson E. Colombini M. J. Biol. Chem. 1994; 269: 1614-1616Abstract Full Text PDF PubMed Google Scholar) and with mitochondria isolated from potato tubers (13.Lee A.C. Zizi M. Colombini M. J. Biol. Chem. 1994; 269: 30974-30980Abstract Full Text PDF PubMed Google Scholar), it was suggested that cytosolic NADH produced by glycolysis could close the voltage-dependent anionic channel and consequently limit the passage of molecules such as ADP toward the intermembrane space. In permeabilized yeast cells, it has been shown that NADH is not involved in the voltage-dependent anionic channel closure and that in situ produced NADH is channeled through voltage-dependent anionic channel to the intermembrane space, where the external NADH dehydrogenases are located (14.Averet N. Aguilaniu H. Bunoust O. Gustafsson L. Rigoulet M. J. Bioenerg. Biomembr. 2002; 34: 499-506Crossref PubMed Scopus (22) Google Scholar). Another possible effector involved in the Crabtree effect is Ca2+ (15.Evtodienko Y.V. Teplova V.V. Duszyński J. Bogucka K. Wojtczak L. Cell Calcium. 1994; 15: 439-446Crossref PubMed Scopus (22) Google Scholar). In Ehrlich ascites tumors and in Zajdela hepatoma cells, it has been observed that there is a glucose-induced increase in cytoplasmic calcium levels along with an enhanced mitochondrial uptake of this cation. Inside the mitochondria, Ca2+ would inhibit ATP synthase by enhancing the interaction with IF1, its inhibitory subunit (16.Wojtczak L. Teplova V.V. Bogucka K. Czyz A. Makowska A. Wieckowski M.R. Duszynski J. Evtodienko Y.V. Eur. J. Biochem. 1999; 263: 495-501Crossref PubMed Scopus (41) Google Scholar). However, is not clear whether this Ca2+ accumulation is a common event in all Crabtree-positive cells, since in AS-D30 hepatoma cells, calcium levels are not modified after glucose addition (7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar). Thus, to date, no clear experimental results have allowed determination of the early event leading to the Crabtree effect. With regard to this Crabtree effect, yeast species are either negative (e.g. Candida utilis) or positive (e.g. Saccharomyces cerevisiae). Yeast thus constitutes a good experimental model to study this effect. Under its alternative designation of glucose repression, the Crabtree effect has indeed been thoroughly studied in S. cerevisiae, in which short term and long term events have been defined. Regarding the latter class of events, when S. cerevisiae grows using high glucose concentrations as carbon source, it represses oxidative metabolism by down-regulating the synthesis of mitochondrial respiratory chain components and by inhibiting enzymatic activities of the Krebs and glyoxylate cycles. At the same time, the expression of glycolytic enzymes is enhanced (reviewed in Ref. 17.Gancedo J.M. Microbiol. Mol. Biol. Rev. 1998; 62: 334-361Crossref PubMed Google Scholar). Whereas long term effects have been thoroughly studied and are very well understood, the origin of the short term events is ill defined. It has been proposed that during glucose repression, metabolic intermediates could have a regulatory role in both short and long term events, functioning as “metabolic messengers” (18.Thevelein J.M. Yeast. 1994; 10: 1753-1790Crossref PubMed Scopus (314) Google Scholar). For instance, in mutants that accumulate different glycolysis metabolites, the transcription of glycolytic genes increases, pointing to a relationship between internal metabolite levels and enzyme expression (19.Muller S. Boles E. May M. Zimmermann F.K. J. Bacteriol. 1995; 177: 4517-4519Crossref PubMed Google Scholar) (e.g. glucose phosphorylation to glucose 6-phosphate (G6P) 4The abbreviations used are: G6P, glucose 6-phosphate; T6P, trehalose 6-phosphate; F6P, fructose 6-phosphate; JO2, respiratory flux; F16bP, fructose 1,6-bisphosphate. seems to be important for signaling processes induced by glucose L. P. Boles E. M. J.M. J. Yeast 2001; Google Scholar, S. J.M. J. E. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, R. S. E. 2002; PubMed Scopus Google trehalose 6-phosphate the glycolytic flux by activity R. C. J.M. 1993; PubMed Scopus Google a yeast that trehalose 6-phosphate synthase glycolysis hexose phosphates in to glucose J.M. S. Biochem. 1995; 20: Full Text PDF PubMed Scopus Google Scholar). However, it has not been clearly whether metabolic intermediates could as in long or short term regulatory In S. cerevisiae, cytoplasmic levels of glycolysis hexose phosphates increase after glucose addition to the culture J.A. A. J.A. K. Yeast 2002; Google Scholar, C. J. J. J.M. Yeast. 1998; PubMed Scopus Google Scholar). the possible role of glycolysis intermediates as metabolic we whether some of these could to the short term Crabtree effect as signaling molecules during glucose-induced of oxidative In to study such a we of the of Crabtree-positive and utilis) yeast In both of isolated mitochondria, we found that low, physiological concentrations of and fructose 6-phosphate stimulated the respiratory flux and this effect was strongly antagonized by fructose 1,6-bisphosphate (F16bP). On the other hand, F16bP by itself inhibited mitochondrial respiration only in mitochondria isolated from S. We also observed that in the yeast which F16bP in to glucose addition, the Crabtree effect is enhanced as with the strain. F16bP-mediated inhibition of respiratory flux was also observed in isolated rat liver these results and taking into account that F16bP in the cell conditions, we propose that F16bP has an effector role in the of oxidative metabolism observed in the of the Crabtree effect. Yeast and cerevisiae an and C. used for mitochondria obtained by cells in yeast with as carbon source, Yeast cells in for spheroplasts and mitochondria The can and can A. Bunoust O. Rigoulet M. J.M. Eur. J. Biochem. PubMed Scopus Google Scholar) in yeast with as carbon and at of and obtained to N. Bunoust O. Rigoulet M. Guerin B. Mol. Biochem. 1998; PubMed Google Scholar) and in and Yeast mitochondria isolated from spheroplasts as B. P. M. PubMed Scopus Google Scholar), and in liver mitochondria obtained to A. S. Biochem. 1990; PubMed Scopus Google Scholar) from and in determination was using the with as a of was in a at with a to a of or mitochondria of in or NADH for mitochondria or for or was used as respiratory For rat liver mitochondria, was In to spheroplasts for with at For mitochondria of in the presence of of and ADP was added at the in the cells and or cells and C. utilis) in in an of of in in the presence of and as respiratory isolated S. cerevisiae mitochondria not have a T. K. B. J. Biol. Chem. Full Text PDF PubMed Google Scholar) internal and external NADH dehydrogenases that to the the in these is of the changes at in a The of was from the of as a of of was of by was from of the R. PubMed Scopus Google Scholar). mitochondria in the mitochondrial with in the presence of as respiratory The at was with a at The was and was at and by was a with and and and through and of phosphates was a with a to Ref. L. J. Yeast. PubMed Scopus Google In yeast cells, the addition of of glucose results in a metabolic toward and in the accumulation of glycolysis hexose phosphates J.A. A. J.A. K. Yeast 2002; Google Scholar, C. J. J. J.M. Yeast. 1998; PubMed Scopus Google Scholar). accumulation of hexose phosphates with an inhibition of we the of a role of these intermediates in the regulation of mitochondrial oxidative one of the glycolysis hexose phosphates F6P, and was the effect of G6P, F6P, and F16bP respiration. The respiration was stimulated in a in the presence of and the by was it be that cytosolic concentrations from to have been concentrations of are not and only the induced by to is In the presence of F6P, this increase was and for physiological concentrations there was no effect. On the other hand, F16bP, at physiological concentrations J.A. A. J.A. K. Yeast 2002; Google Scholar, C. J. J. J.M. Yeast. 1998; PubMed Scopus Google Scholar, R. H. C. Yeast. PubMed Scopus Google Scholar) induced an inhibition of the respiratory that This effect is not the respiratory since the same effect was also observed when using as of NADH not Under phosphorylation conditions, and no effect the respiratory whereas the inhibition in the presence of F16bP was observed This that the F16bP-mediated inhibition is of the respiratory of hexose phosphates the respiratory flux of isolated yeast mitochondria and respiratory the same as in that ADP was after the addition of concentrations of glucose 6-phosphate fructose 6-phosphate and fructose 1,6-bisphosphate as are as of In to whether the by and was to the mitochondrial potential was in the presence of glycolysis hexose to the addition of either or not the potential Furthermore, the not to F16bP and slightly decreased the addition of F16bP these the of a possible effect induced by and was The F16bP-mediated decrease of the respiratory in either the to decrease in strongly suggested that at one of the mitochondrial respiratory is potential in the presence of hexose in a the fermentative hexose phosphate increases in the Thus, the mitochondria are in the presence of all of these at the same we whether the of the respiratory could be inhibited by F16bP. was by F16bP the F16bP inhibition was of of of of This that physiological conditions, the effect of glycolysis hexose phosphates oxidative phosphorylation is that of F16bP an inhibition of the respiratory and in of the results observed for flux and in the presence of hexose phosphate we the respiratory chain activity is by these hexose an of the respiratory chain and has been as an important for the respiratory both in and J.P. E. Rigoulet M. Guerin B. Scopus Google Scholar, M. Guerin B. M. Eur. J. Biochem. PubMed Scopus Google Scholar). activity is strongly inhibited by F16bP This which is of the respiratory is important at concentrations and of inhibition for F16bP. Furthermore, and no effects activity not We activity in the presence of these glycolysis hexose stimulated the activity of This was for both hexose a at of the However, this was obtained for concentrations of these and only a was observed in the presence of physiological and concentrations of hexose inhibition was also observed this respiratory Furthermore, hexose effects shown in to not that the was indeed by hexose and F16bP and inhibitory effects activity we to whether these effects could be observed the isolated Indeed, of could be by F16bP, and activity was this we have used mitochondria isolated from S. cerevisiae as an experimental However, to results to the in it was to study mitochondria in a physiological that has been used to in situ is the of permeabilized cells N. Bunoust O. Rigoulet M. Guerin B. Mol. Biochem. 1998; PubMed Google Scholar, C. S. Rigoulet M. Biochem. 1995; PubMed Scopus Google Scholar). spheroplasts have been to study yeast metabolism N. Bunoust O. 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In of these cases, it was found that closure of the voltage-dependent channel was for flux to the intermembrane (14.Averet N. Aguilaniu H. Bunoust O. Gustafsson L. Rigoulet M. J. Bioenerg. Biomembr. 2002; 34: 499-506Crossref PubMed Scopus (22) Google Scholar, E. A. E. C. Biochem. 1995; PubMed Scopus Google Scholar). the voltage-dependent anionic channel is in permeabilized it is possible that the hexose is to this would also that F16bP would be channeled through the outer membrane in permeabilized phosphate in the different in a F16bP been shown to mitochondrial oxidative phosphorylation in it was to respiration of cells in where F16bP We thus induced the Crabtree effect in cells and in the which the enzyme trehalose 6-phosphate have that this glycolysis hexose F16bP, in to glucose addition J.M. S. Biochem. 1995; 20: Full Text PDF PubMed Scopus Google Scholar, S. W. R. J. J.M. 1993; 23: PubMed Scopus Google Scholar, L. S. Zimmermann F.K. J.M. J. 10: PubMed Scopus (106) Google Scholar). and respiration decreased in the Furthermore, when the of respiration inhibition for glucose addition inhibited by and the respiration of and strains, We the of of the hexose phosphates after glucose that in the the of both and not after glucose On the other hand, the of F16bP In the there is a increase in the of and and a increase in F16bP into account that F16bP the respiratory flux of isolated mitochondria, permeabilized and cells, we propose that the accumulation of F16bP is for the observed between the two and in the observed of glucose-induced inhibition of Crabtree effect is enhanced in the yeast in a In some yeast where glucose does not glucose addition does not inhibit respiration (4.Van Urk H. Voll W.S. Scheffers W.A. Van Dijken J.P. Appl. Environ. Microbiol. 1990; 56: 281-287Crossref PubMed Google Scholar, Dijken J.P. 1993; PubMed Scopus Google Scholar). C. is one such The respiratory activity of cells was not by the addition of glucose whereas the concentrations of and and that of F16bP was In mitochondria isolated from C. and stimulated the respiratory This effect is by F16bP. it is that there was no F16bP-mediated inhibition of the respiratory chain in isolated mitochondria This that the respiration inhibition by F16bP a role in the glucose-induced Crabtree effect. In it has been that hepatoma cells a Crabtree effect with a increase in cytoplasmic F16bP (7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar). This metabolite can a cytosolic between and (7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar, A. S. M. M. Moreno-Sanchez R. J. 2006; PubMed Scopus Google Scholar). We thus whether the F16bP-mediated inhibition could also in isolated mammalian this accumulation was important for the glucose-induced of respiratory since we able to inhibit the respiration of mitochondria from a rat liver using concentrations with found in hepatoma cells. respiration was inhibited by F16bP that this is in the Crabtree effect in mammalian cells. Furthermore, whereas and by no effects the mitochondrial respiratory the inhibition was slightly decreased in presence In aerobic organisms, the phosphate potential is both through the glycolytic and respiratory to the mitochondrial respiratory In the presence of high concentrations of aerobic metabolism toward a of the The glucose-induced toward associated with respiration inhibition was named the “Crabtree effect.” in the different hypotheses have been laid and no clear to all Crabtree-positive cells. It has been that this phenomenon is induced by different such as changes in the phosphate potential or in (7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar). Indeed, since glycolytic and respiratory both the phosphate it is possible that changes in ATP or Pi could the phosphorylation in aerobic In this during the Crabtree effect in hepatoma cells (7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar) and in yeast Hollander J.A. Ugurbil K. Brown T.R. Shulman R.G. Biochemistry. 1981; 20: 5871-5880Crossref PubMed Scopus (176) Google Scholar), a glucose-induced decrease of cytoplasmic phosphate has been a cytoplasmic accumulation of fructose 1,6-bisphosphate has been as well for Ehrlich and yeast Crabtree-positive cells (7.Rodriguez-Enriquez S. Juarez O. Rodriguez-Zavala J.S. Moreno-Sanchez R. Eur. J. Biochem. 2001; 268: 2512-2519Crossref PubMed Scopus (106) Google Scholar, J.A. A. J.A. K. Yeast 2002; Google Scholar, B. B. J. Biol. Chem. Full Text PDF PubMed Google Scholar). in yeast cells, it has been that the addition of glucose induced an increase in cytosolic F16bP from to in a G. Shulman R.G. T. T.R. J. Biochemistry. PubMed Scopus Google Scholar), which is in good with concentrations in this in a this increases glucose addition In mammalian cells and this metabolite a cytosolic However, in hepatoma cells, this is and to L. S. Zimmermann F.K. J.M. J. 10: PubMed Scopus (106) Google Scholar). This is clearly the of concentrations used in this Thus, in this we clearly that the mitochondrial respiratory is inhibited by physiological concentrations of F16bP both in and This is for both isolated mitochondria and permeabilized spheroplasts from the Crabtree-positive yeast S. the respiratory when hexose and are used the effect is an inhibition of the respiratory by F16bP. We have shown that through was slightly inhibited by F16bP and that this metabolite inhibited results to an in F16bP-mediated regulation of the mitochondrial respiratory This effect seems to Crabtree-positive yeast Indeed, in mitochondria isolated from the species C. hexose are able to the respiratory and this is inhibited by F16bP. However, in this the respiratory itself is inhibited by F16bP. these results that in yeast, F16bP participates in the Crabtree effect. We clearly that F16bP induces an inhibition of the respiratory two of the mitochondrial respiratory We propose that in this hexose as an of the respiratory Indeed, we to that this in the that the respiration of cells that accumulate F16bP to different changes It has been shown that the of of the of which has levels of F16bP, is not inhibited by high glucose concentrations J.A. A. J.A. K. Yeast 2002; Google Scholar, J.A. J.A. Van K. Appl. Environ. Microbiol. 2001; PubMed Scopus Google Scholar). has Biochemistry. PubMed Scopus Google Scholar). Furthermore, the well for hexose phosphates J.M. S. Biochem. 1995; 20: Full Text PDF PubMed Scopus Google Scholar, C. J. J. J.M. Yeast. 1998; PubMed Scopus Google Scholar, S. W. R. J. J.M. 1993; 23: PubMed Scopus Google Scholar, L. S. Zimmermann F.K. J.M. J. 10: PubMed Scopus (106) Google Scholar), has an enhanced Crabtree effect and In mammalian cells, we have that physiological concentrations of F16bP inhibited the respiration of isolated rat liver mitochondria as of the early the Crabtree effect in cells was the of oxidative phosphorylation (reviewed in Ref. R. S. A. E. J. Scopus Google Scholar). This was by the that hepatoma cells phosphate potential through respiration S. Moreno-Sanchez R. Biochem. PubMed Scopus Google Scholar). results to the that an of mitochondrial is not a for Crabtree effect since the same of respiration by F16bP can be observed in mitochondria obtained from a is hexose phosphate that seems to have an mitochondrial N. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). The presence of this is important for the of and for enhancing the of N. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). Thus, the of hexose phosphates as metabolic and cell oxidative metabolism to be In we propose that F16bP as a metabolic a decrease in respiratory flux during the transition to fermentative metabolism in the of the Crabtree F16bP accumulation be one of events (e.g. changes in or phosphate that to this inhibition of respiration. We J. for the of the and O. Bunoust for We C. for the