Showing papers on "Phosphofructokinase activity published in 1990"
TL;DR: The relative activities of hexokinase and 6-phosphofructokinase suggest that, particularly in neoplastic cells, in which the capacity for glucose transport is high, Hexokinase could approach saturation in respect to intracellular glucose; consequently, hexokin enzyme and phosphofructkinase could play an important role in the regulation of glycolytic flux in these cells.
Abstract: 1. Maximal activities of some key enzymes of glycolysis, the pentose phosphate pathway, the tricarboxylic acid cycle and glutaminolysis were measured in homogenates from a variety of normal, neoplastic and suppressed cells. 2. The relative activities of hexokinase and 6-phosphofructokinase suggest that, particularly in neoplastic cells, in which the capacity for glucose transport is high, hexokinase could approach saturation in respect to intracellular glucose; consequently, hexokinase and phosphofructokinase could play an important role in the regulation of glycolytic flux in these cells. 3. The activity of pyruvate kinase is considerably higher in tumorigenic cells than in non-tumorigenic cells and higher in metastatic cells than in tumorigenic cells: for non-tumorigenic cells the activities range from 28.4 to 574, for tumorigenic cells from 899 to 1280, and for metastatic cells from 1590 to 1627 nmol/min per mg of protein. 4. The ratio of pyruvate kinase activity to 2 x phosphofructokinase activity is very high in neoplastic cells. The mean is 22.4 for neoplastic cells, whereas for muscle from 60 different animals it is only 3.8. 5. Both citrate synthase and isocitrate dehydrogenase activities are present in non-neoplastic and neoplastic cells, suggesting that the full complement of tricarboxylic-acid-cycle enzymes are present in these latter cells. 6. In neoplastic cells, the activity of glutaminase is similar to or greater than that of hexokinase, which suggests that glutamine may be as important as glucose for energy generation in these cells.
193 citations
TL;DR: Data show that both glycolytic and glycogenolytic fluxes are increased in the hyperthyroid rat heart, necessary to cope with the increased number and activity of Na+/K(+)-ATPase pumps that occur in response to thyroxine treatment.
56 citations
Journal Article•
TL;DR: In liver homogenates from untreated rats, increasing concentrations of aluminum did not show any appreciable effect on hexokinase or glucokinase activity but did cause progressive decreases in phosphofructokinase Activity, suggesting that aluminum-induced inhibition of liver phosphofructureokinase, an important control site in the glycolytic pathway, is most likely responsible for aluminum- induced inhibition of hepatic Glycolysis.
Abstract: Aluminum, an abundant element in the earth's crust, has been implicated in various pathological disorders and low concentrations of this element have recently been shown to inhibit brain glycolysis. However, despite the fact that aluminum accumulates in high concentrations in the liver, potential effects of this metal on hepatic intermediary metabolism have not been explored. In perfused livers from untreated rats, maximal rates of production of lactate plus pyruvate (glycolysis) were 93 +/- 15 mumols/g/hr. Glycolysis was severely inhibited in livers from aluminum-treated rats (0.5 mg/kg, 6 hr before experiment) with maximal rates of only 23 +/- 4 mumols/g/hr. In contrast, glucose production (glycogenolysis) and hepatic oxygen uptake were not altered significantly by prior treatment with aluminum. In livers from fasted rats, pretreatment with aluminum did not influence gluconeogenesis or production of lactate and pyruvate from fructose (5 mM). This finding indicates that pyruvate kinase is not inhibited by aluminum and implicates phosphofructokinase, hexokinase and/or glucokinase as sites for the inhibitory effect of aluminum on glycolysis. In liver homogenates from untreated rats, increasing concentrations of aluminum did not show any appreciable effect on hexokinase or glucokinase activity but did cause progressive decreases in phosphofructokinase activity. Therefore, aluminum-induced inhibition of liver phosphofructokinase, an important control site in the glycolytic pathway, is most likely responsible for aluminum-induced inhibition of hepatic glycolysis.
32 citations
TL;DR: It is concluded that autocatalytic activation of phosphofructokinase by fructose-1,6-P2, but not by glucose-1+, may nevertheless play a role in facilitating the initiation of the oscillations and in modulating their frequency.
32 citations
TL;DR: Evidence is presented which suggests that the alkaline isoenzyme of FBPase, which is widely regarded as a laboratory artefact, may have an important role in vivo in the regulation and control of glycolysis and gluconeogenesis.
Abstract: The regulatory properties of human liver and muscle fructose-1,6-bisphosphatases (FBPase) have been studied in control tissues obtained at autopsy and in tissues from a neonate with FBPase deficiency who died as a result of an overwhelming acidosis. Evidence is presented which suggests that the alkaline isoenzyme of FBPase, which is widely regarded as a laboratory artefact, may have an important role in vivo in the regulation and control of glycolysis and gluconeogenesis. FBPase exhibits the hysteretic and dissociative properties associated with regulatory enzymes, and many of the factors which effect FBPase have inverse effects on phosphofructokinase activity, thus providing an integrated regulatory cycle for the control of the direction and rate of flux through the glycolytic pathway.
13 citations
TL;DR: The findings suggest that diabetes affects the age-associated evolution of retrograde transport, presumably a reflection of the neuropathy occurring in the distal axon branches, without altering anterograde transport to any appreciable extent.
Abstract: Phosphofructokinase activity was measured in the sciatic nerve of streptozotocin-induced diabetic and nondiabetic rats. Average steady-state phosphofructokinase activity was obtained from three consecutive segments of the mid-femoral region in the left sciatic nerve in both diabetic (4 and 24 weeks) and nondiabetic, age-matched animals. Over time, phosphofructokinase activity significantly decreased (p less than 0.05) with diabetes, with no effect demonstrated within similar age-groups. The accumulation of phosphofructokinase activity was accomplished by ligating the mid-femoral region of the right sciatic nerve for 24 h. Anterograde and retrograde axonal transport of phosphofructokinase was measured in the 3-mm segment proximal and distal to the ligature, respectively. There was a trend (p = 0.0627) towards a decline in net proximal accumulation (mean proximal minus mean background) with age. Net distal (mean distal minus mean background) activity declined by 80% (p less than 0.05) in the control group between 4 and 24 weeks of the diabetic state. However, diabetic animals did not experience the same age-related decline in retrograde transport. The findings suggest that diabetes affects the age-associated evolution of retrograde transport, presumably a reflection of the neuropathy occurring in the distal axon branches, without altering anterograde transport to any appreciable extent.
4 citations
Journal Article•
TL;DR: The effect of pH on the phosphofructokinase activity from the posterior adductor muscle of the sea mussel Mytilus galloprovincialis Lmk, is dependent on the concentrations of MgATP2- and free ATP as mentioned in this paper.
Abstract: The effect of pH on the phosphofructokinase activity from the posterior adductor muscle of the sea mussel Mytilus galloprovincialis Lmk., is dependent on the concentrations of MgATP2- and free ATP. Reducing pH from pH 8.0 to pH 6.9 alters the equilibria among the various forms of free ATP, greatly increasing the concentration of HATP3-, without apparent change of ATP4- concentrations. The concentration of HATP3- correlates well with the data that indicates the marked inhibition of the phosphofructokinase activity that occurs on lowering pH, suggesting that the HATP3- may be the responsible for the inhibition.
3 citations