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Borza T, Iancu CV, Pike E, Honzatko RB, Fromm HJ. Variations in the response of mouse isozymes of adenylosuccinate synthetase to inhibitors of physiological relevance. J Biol Chem 2003; 278:6673-9. [PMID: 12482871 DOI: 10.1074/jbc.m210838200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vertebrates have acidic and basic isozymes of adenylosuccinate synthetase, which participate in the first committed step of de novo AMP biosynthesis and/or the purine nucleotide cycle. These isozymes differ in their kinetic properties and N-leader sequences, and their regulation may vary with tissue type. Recombinant acidic and basic synthetases from mouse, in the presence of active site ligands, behave in analytical ultracentrifugation as dimers. Active site ligands enhance thermal stability of both isozymes. Truncated forms of both isozymes retain the kinetic parameters and the oligomerization status of the full-length proteins. AMP potently inhibits the acidic isozyme competitively with respect to IMP. In contrast, AMP weakly inhibits the basic isozyme noncompetitively with respect to all substrates. IMP inhibition of the acidic isozyme is competitive, and that of the basic isozyme noncompetitive, with respect to GTP. Fructose 1,6-bisphosphate potently inhibits both isozymes competitively with respect to IMP but becomes noncompetitive at saturating substrate concentrations. The above, coupled with structural information, suggests antagonistic interactions between the active sites of the basic isozyme, whereas active sites of the acidic isozyme seem functionally independent. Fructose 1,6-bisphosphate and IMP together may be dynamic regulators of the basic isozyme in muscle, causing potent inhibition of the synthetase under conditions of high AMP deaminase activity.
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Affiliation(s)
- Tudor Borza
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 5011, USA
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2
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Bruton JD, Wretman C, Katz A, Westerblad H. Increased tetanic force and reduced myoplasmic [P(i)] following a brief series of tetani in mouse soleus muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 272:C870-4. [PMID: 9124522 DOI: 10.1152/ajpcell.1997.272.3.c870] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Muscle performance is improved after a brief period of exercise (warm-up). One factor that is known to strongly affect force production is the myoplasmic concentration of inorganic phosphate ([P(i)]). Improved performance after warm-up may therefore be due to a reduction of [P(i)]. Herein, we show that after a warm-up protocol (15 tetani at 2-s intervals), tetanic force is increased by approximately 6% (P < 0.05) and [P(i)] is almost halved (P < 0.05) in isolated mouse soleus muscle. A warm-up protocol with longer intervals (15 tetani at 5-s intervals) reduced tetanic force and did not alter [P(i)]. We conclude that a reduction of [P(i)] contributes to the force-potentiating effect of warm-up.
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Affiliation(s)
- J D Bruton
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
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3
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Andrés V, Carreras J, Cussó R. Myofibril-bound muscle phosphofructokinase is less sensitive to inhibition by ATP than the free enzyme, but retains its sensitivity to stimulation by bisphosphorylated hexoses. Int J Biochem Cell Biol 1996; 28:1179-84. [PMID: 8930143 DOI: 10.1016/1357-2725(96)00046-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Phosphofructokinase activity is modulated by allosteric effectors and macromolecular interactions (e.g. binding to myofibrillar components). The aim of this study was to determine the effects of ATP and bisphosphorylated sugars upon phosphofructokinase in the presence of myofibrils. Myofibrils were prepared from resting and electrically stimulated rat muscle. Dephosphorylation of myofibrils was performed with alkaline phosphatase acid. Purified rabbit skeletal muscle phosphofructokinase was used for all experiments. Myofibrils from resting muscle showed a higher capacity to bind phosphofructokinase and a lower phosphate content than myofibrils from stimulated muscle. Dephosphorylation of myofibrils did not increase their binding capacity. Myofibrils greatly counteracted the inhibition of phosphofructokinase by high concentrations of ATP, without affecting maximum activity. In the presence of myofibrils, both glucose 1,6-bisphosphate and fructose 2,6-bisphosphate additionally activated muscle phosphofructokinase. We suggest that the binding of phosphofructokinase to myofibrils in combination with increasing glucose 1,6-bisphosphate concentration could be important in the enhancement of the glycolytic flux that takes place during muscle contraction.
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Affiliation(s)
- V Andrés
- Unitat de Bioquimica, Facultat de Medicina, Universitat de Barcelona, Spain
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Skalecki K, Mularczyk W, Dzugaj A. Kinetic properties of D-fructose-1,6-bisphosphate 1-phosphohydrolase isolated from human muscle. Biochem J 1995; 310 ( Pt 3):1029-35. [PMID: 7575399 PMCID: PMC1135998 DOI: 10.1042/bj3101029] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
D-Fructose-1,6-bisphosphate 1-phosphohydrolase (EC 3.1.3.11) [Fru(1,6)Pase] was isolated from human muscle in an electrophoretically homogeneous form, free of aldolase contamination. The enzyme is inhibited by the substrate [fructose (1,6)-bisphosphate]. Km is 0.77 microM; Kis is 90 microM. The fructose-2,6-bisphosphate [Fru(2,6)P2], a regulator of gluconeogenesis, inhibits human muscle Fru(1,6)Pase with Ki = 0.13 microM. To determine Km, Kis and Ki the integrated method was used. AMP is an allosteric inhibitor of Fru(1,6)Pase. As with other mammalian isoenzymes, the human muscle enzyme is more strongly inhibited by AMP than is the liver isoenzyme [Dzugaj and Kochman (1980) Biochim. Biophys. Acta 614, 407-412]. Both of the inhibitors [AMP and Fru(2,6)P2] act synergistically on human muscle Fru(1,6)Pase. Ki for Fru(2,6)P2 determined in the presence of 0.4 microM AMP was 0.028 microM. The human muscle enzyme, like other mammalian Fru(1,6)Pases, requires Mg2+ for its activity. The Ka for magnesium was 232 microM, and h (Hill coefficient) = 2.0.
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Affiliation(s)
- K Skalecki
- Department of Animal Physiology, University of Wrocław, Poland
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5
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Green HJ, Cadefau J, Cussó R, Ball-Burnett M, Jamieson G. Metabolic adaptations to short-term training are expressed early in submaximal exercise. Can J Physiol Pharmacol 1995; 73:474-82. [PMID: 7671190 DOI: 10.1139/y95-060] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In previous studies we have been able to demonstrate tighter metabolic control of muscle metabolism during prolonged steady-state exercise 5 to 6 days after the initiation of training and well before changes in oxidative potential. To examine whether the metabolic adaptations are manifested during the non-steady-state adjustment to submaximal exercise, 11 male subjects (Vo2 peak, 45 +/- 2.4 mL.kg(-1). min(-1), X +/- SE) performed 98 min of cycle exercise at 67% of Vo2 peak prior to and following 3 to 4 days of training for 2 h per day. Analysis of lactate concentration (mmol/kg dry weight) in samples rapidly extracted from vastus lateralis indicated reductions (p < 0.05) of 44% at 3 min ( 42.1 +/- 7.1 vs. 23.6 +/- 7.7), 29% at 15 min (35.4 +/- 6.4 vs. 25.0 +/- 6.0), and 32% at 98 min (22.9 +/- 6.9 vs. 15.6 +/- 3.2) with training. Training also resulted in higher phosphocreatine and lower creatine and P(i) values that were not specific to any exercise time point. In addition, Vo2 was not altered either during the non-steady state or during the steady-state phases of exercise. These results suggest that at least part of the tightening of the metabolic control and the apparent reduction in glycogenolysis and glycolysis in response to short-term training occurs during the adjustment phase to steady-state exercise.
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Affiliation(s)
- H J Green
- Department of Kinesiology, University of Waterloo, Canada
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Tarui S. Glycolytic defects in muscle: aspects of collaboration between basic science and clinical medicine. Muscle Nerve 1995; 3:S2-9. [PMID: 7603522 DOI: 10.1002/mus.880181404] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The molecular heterogeneities of enzyme abnormality have been identified successfully since 1990 for major clinical entities of glycogenolytic and glycolytic defects in skeletal muscle. The interchange between clinical medicine and basic science, which enabled these achievements, has a long history. This review introduces several important examples of this interchange, which has borne much fruit in the comprehensive understanding of glycogenolysis-glycolysis in skeletal muscle and the related defects that cause various metabolic diseases. For instance, the presence of "glycogen synthase" was mainly suggested by the pathophysiology of McArdle's disease. Clinical manifestations of muscle phosphofructokinase (PFK) deficiency have indicated that there could be PFK isozymes under separate genetic control. Although glycolysis is a unidirectional pathway, enzyme defects at each step do not necessarily cause similar manifestations. Glycogen accumulation is mostly associated with enzyme defects in glycogenolysis and in the first stage of glycolysis. Since the original report of phosphoglycerate mutase deficiency in 1981, no newly recognized glycolytic defects have been presented. Glycolytic steps for which no enzyme deficiency has been identified seem to provide another important impetus for further study of "fail-safe" mechanisms in regard to monogenic disorders.
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Affiliation(s)
- S Tarui
- Department of Internal Medicine, Otemae Hospital, Osaka, Japan
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Beitner R. Control of glycolytic enzymes through binding to cell structures and by glucose-1,6-bisphosphate under different conditions. The role of Ca2+ and calmodulin. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1993; 25:297-305. [PMID: 8462719 DOI: 10.1016/0020-711x(93)90616-m] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- R Beitner
- Department of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
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Bassols A, Andrés V, Ballarín M, Mahy N, Carreras J, Cussó R. Identification of guanine and adenine nucleotides as activators of glucose-1,6-bisphosphatase activity from rat skeletal muscle. Arch Biochem Biophys 1991; 291:121-5. [PMID: 1656884 DOI: 10.1016/0003-9861(91)90113-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Glucose-1,6-bisphosphatase activity in rat skeletal muscle extracts was lost after exhaustive dialysis or precipitation with ammonium sulfate. Most of the original activity was recovered when the boiled extract was added to the ammonium sulfate precipitate. Qualitative analysis of the boiled extract revealed that the activator was either a nucleoside or a nucleotide. The results show that at concentrations between 0.05 and 1 mM, only guanine and adenosine derivatives are effective as activators, the former being more powerful. However, only guanosine, ADP, and AMP have an activating effect at the concentrations found in the boiled extract. The results of assays in vitro suggest that adenine nucleotides could be physiological modulators of glucose-1,6-bisphosphatase activity during muscle contraction.
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Affiliation(s)
- A Bassols
- Unitat de Bioquímica, Facultat de Medicina, Universitat de Barcelona, Zona Universitària Pedralbes, Spain
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Winder WW, Fisher SR, Gygi SP, Mitchell JA, Ojuka E, Weidman DA. Divergence of muscle and liver fructose 2,6-diphosphate in fasted exercising rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1991; 260:E756-61. [PMID: 2035632 DOI: 10.1152/ajpendo.1991.260.5.e756] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Previous studies demonstrate that nonexercising muscle may serve as a source of lactate for hepatic gluconeogenesis during long-term exercise. The concentration of fructose 2,6-diphosphate (F-2,6-P2), a signal molecule that accelerates glycolysis, was examined in liver and muscles of fed and fasted resting rats and in fasted rats run for 5, 15, or 30 min at 21 m/min (15% grade). Liver F-2,6-P2 decreased in response to fasting and exercise. White quadriceps (composed predominantly of type IIb fibers) F-2,6-P2 increased from 2.2 +/- 0.1 to 4.5 +/- 0.4 pmol/mg in the fasted rats in response to 30 min of treadmill running. No increase was observed in the red region of the quadriceps (composed of type IIa fibers). The fasted rats also exhibited a threefold increase in glucose 1,6-diphosphate (G-1,6-P2) in the white quadriceps after 30 min of exercise, whereas no significant changes were observed in the red quadriceps or in liver. The increases in F-2,6-P2 and G-1,6-P2 may be important in accelerating glycolysis and enhancing lactate production in muscles that are not glycogen depleted during long-term exercise.
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Affiliation(s)
- W W Winder
- Zoology Department, Brigham Young University, Provo, Utah 84602
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10
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Green HJ, Cadefau J, Pette D. Altered glucose 1,6-bisphosphate and fructose 2,6-biphosphate levels in low-frequency stimulated rabbit fast-twitch muscle. FEBS Lett 1991; 282:107-9. [PMID: 2026244 DOI: 10.1016/0014-5793(91)80455-c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Glucose 1,6-bisphosphate (Glc-1,6-P2) and fructose 2,6-bisphosphate (Fru-2,6-P2) concentrations display pronounced increases in rabbit fast-twitch muscle during chronic low-frequency stimulation. These increases are first seen after stimulation periods exceeding 3 h and reach maxima after 12-24 h of stimulation (approximately 3-fold for Glc-1,6-P2 and 5-fold for Fru-2,6-P2). Both metabolites regress to normal values after stimulation periods longer than 4 days. The fact that their increases coincide with the replenishment of glycogen after its initial depletion, could point to a role of Glc-1,6-P2 and Fru-2,6-P2 in glycogen metabolism.
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Affiliation(s)
- H J Green
- Fakultät für Biologie, Universität Konstanz, Germany
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11
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Katz A, Sahlin K, Broberg S. Regulation of glucose utilization in human skeletal muscle during moderate dynamic exercise. THE AMERICAN JOURNAL OF PHYSIOLOGY 1991; 260:E411-5. [PMID: 2003594 DOI: 10.1152/ajpendo.1991.260.3.e411] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effect of bicycle exercise (75% of maximal oxygen uptake) on glucose uptake by the inferior limb (LGU) and glycolysis in human skeletal muscle has been investigated. Biopsies were obtained from the quadriceps femoris muscle before exercise, after 5 and 40 min of exercise, and at fatigue [74.9 +/- 4.7 (SE) min]. LGU was 0.05 +/- 0.02 mmol/min at rest, increased approximately sevenfold after 5 min of exercise, and continued to increase linearly during the first 40 min of exercise. Thereafter LGU stabilized at approximately 1.4 mmol/min until fatigue. Intracellular glucose was low at rest but increased sixfold after 5 min of exercise (P less than 0.01 vs. rest); thereafter, intracellular glucose decreased and was not significantly different from the value at rest after 40 min or at fatigue (P greater than 0.05). D-Glucose 6-phosphate (G-6-P) and alpha-D-glucose 1,6-bisphosphate (G-1,6-P2) (inhibitors of hexokinase) increased significantly after 5 min of exercise (approximately 300% G-6-P; approximately 25% G-1,6-P2) and then decreased continuously. The muscle glycolytic rate (glycogenolysis + glucose uptake) averaged 7.7 mmol.kg dry wt-1.min-1 during the first 40 min of exercise and 3.7 mmol.kg dry wt-1.min-1 during the last 35 min of exercise. The contribution of extracellular glucose to muscle glycolysis was estimated to be only 5 and 19% during the initial and latter phases of exercise, respectively. It is concluded that, during the initial phase of exercise, glucose utilization is limited by phosphorylation, probably due to G-6-P-dependent inhibition of hexokinase.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Katz
- Department of Kinesiology, University of Illinois, Urbana 61801
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12
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Oscillatory synthesis of glucose 1,6-bisphosphate and frequency modulation of glycolytic oscillations in skeletal muscle extracts. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)45757-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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13
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Katz A, Bogardus C. Insulin-mediated increase in glucose 1,6-bisphosphate is attenuated in skeletal muscle of insulin-resistant man. Metabolism 1990; 39:1300-4. [PMID: 2246971 DOI: 10.1016/0026-0495(90)90187-h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The purpose of this study was to determine the effect of insulin infusion on the glucose 1,6-bisphosphate (glucose 1,6-P2) content in skeletal muscle of insulin resistant man. Euglycemic (approximately 100 mg/dL) hyperinsulinemic clamps were performed on seven men with chronically elevated fasting plasma glycemia (228 +/- 13 mg/dL, mean +/- SE) who were insulin resistant (HIR) and five men with normal fasting glycemia (115 +/- 5 mg/dL) who were insulin resistant (NIR). Insulin was infused at successive rates of 40 and 400 mU/m2/min, and biopsies were obtained from the quadriceps femoris muscle before and after insulin infusion. The results were compared with those of normoglycemic insulin-sensitive (NIS) men. The insulin-resistant groups had significantly higher percent body fat values than did the NIS group. Glucose 1,6-P2 increased from 70 +/- 6, 49 +/- 9, and 67 +/- 3 mumols/kg dry weight in the basal state to 135 +/- 12 (P less than .001 v basal), 67 +/- 11 (P greater than .05) and 79 +/- 3 (P greater than .05) after 40 mU insulin in NIS, HIR, and NIR, respectively. Glucose 1,6-P2 increased to 147 +/- 12 (P less than .001 v basal), 91 +/- 15 (P less than .01) and 99 +/- 13 (P less than .05) mumols/kg dry weight after 400 mU insulin in NIS, HIR, and NIR, respectively. The increase in glucose 1,6-P2 in response to 40 mU insulin was only 28% and 18% in HIR and NIR, respectively, of that in NIS.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Katz
- Department of Kinesiology, University of Illinois, Urbana 61801
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Spriet LL. Anaerobic ATP provision, glycogenolysis and glycolysis in rat slow-twitch muscle during tetanic contractions. Pflugers Arch 1990; 417:278-84. [PMID: 2148818 DOI: 10.1007/bf00370993] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Rat soleus muscles were tetanically stimulated in situ with an occluded circulation to examine anaerobic adenosine triphosphate (ATP) provision and the regulation of glycolytic ATP production. Soleus muscles were stimulated for 30-60 s at 1 Hz with 100-200 ms trains (40-80 Hz). Muscles were sampled pre- and post-stimulation for measurements of pH, high energy phosphates and glycolytic intermediates. Total ATP provision by the slow oxidative fibres was 65-121 mumol/g dry muscle and 27-35% of the amount produced by fast glycolytic fibres. Contributions to total ATP provision in the initial 30 contractions were: phosphocreatine, 71%; glycolysis, 28%; and endogenous ATP, 1%. Following 60 contractions the contributions were 45-54%, 44-51% and 2-4%, respectively. During the initial 30 contractions, glycogenolysis (phosphorylase activity) and glycolysis [phosphofructokinase (PFK) activity] were similar as glucose-6-phosphate (G-6-P) and fructose-6-phosphate (F-6-P) did not accumulate. Small accumulations of PFK deinhibitors inorganic phosphate, adenosine diphosphate, adenosine monophosphate and fructose-1,6-diphosphate appeared to account for the PFK activity. In the final 30 contractions, phosphorylase activity increased above PFK as G-6-P and F-6-P accumulated. PFK activity and glycolytic ATP production also increased despite increasing hydrogen ion concentration [H+]. During intense tetanic stimulation of soleus muscle, glycolytic ATP production is initially limited by a low glycogen phosphorylase activity. The activity of PFK increases during in situ contraction through the accumulation of deinhibitors, despite increasing [H+].
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Affiliation(s)
- L L Spriet
- School of Human Biology, University of Guelph, Ontario, Canada
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Andrés V, Carreras J, Cussó R. Regulation of muscle phosphofructokinase by physiological concentrations of bisphosphorylated hexoses: effect of alkalinization. Biochem Biophys Res Commun 1990; 172:328-34. [PMID: 2145837 DOI: 10.1016/s0006-291x(05)80213-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
To clarify the role of glucose-1,6-P2, fructose-2,6-P2 and fructose-1,6-P2 in the control of the glycolytic flux during muscle contraction, we have determined the activity of muscle phosphofructokinase in the presence of physiological concentrations of these bisphosphorylated hexoses and other allosteric effectors, and at increasing pH values. In the presence of fructose-2,6-P2, both glucose-1,6-P2 and fructose-1,6-P2 can additionally activate the enzyme and partially counteract citrate inhibition. Activation of phosphofructokinase produced by alkalinization increases in the presence of the bisphosphorylated hexoses. It is suggested that the hexose bisphosphates could play a significant role in the initial burst of the glycolytic flux during muscle contraction, when an alkaline pH shift is produced.
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Affiliation(s)
- V Andrés
- Unitat de Bioquímica, Facultat de Medicina, Universitat de Barcelona, Spain
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Katz A, Nyomba BL, Bogardus C. Euglycemic hyperinsulinemia increases glucose 1,6-bisphosphate in human skeletal muscle. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1989; 21:1079-82. [PMID: 2684699 DOI: 10.1016/0020-711x(89)90046-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
1. The effects of physiologic concentrations of insulin on the contents of glucose 1,6-bisphosphate (glucose 1,6-P2) and regulators of glucose 1,6-P2 synthase in intact human skeletal muscle have been investigated. 2. Insulin increased glucose 1,6-P2 from a basal value of 70 +/- 6 to 135 +/- 12 mumol/kg dry wt (P less than 0.001). 3. Activation of synthase could not be associated with changes in its inhibitors (fructose 1,6-P2, Pi, citrate) or its substrate glucose 6-P.
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Affiliation(s)
- A Katz
- Clinical Diabetes and Nutrition Section, National Institute of Diabetes, Digestive and Kidney Diseases, Phoenix, AZ 85016
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