Phosphofructokinase activity

Clearly, the activity of phosphofructokinase depends both on ATP and AMP levels and is a function of the cellular energy status. Phosphofructokinase activity is increased when the energy status falls and is decreased when the energy status is high. The rate of glycolysis activity thus decreases when ATP is plentiful and increases when more ATP is needed. 

Table 4.6.17 Assay mixture for assessment of 6-phosphofructokinase activity. Pipette these solutions into 1-ml quartz cuvettes. Instructions for the preparation of these solutions are given in section 4.6.20.3...

Feed-forward regulation In liver, pyruvate kinase is activated by fructose 1,6-bisphosphate, the product of the phosphofructo-kinase reaction. This feed-forward (instead of the more usual feedback) regulation has the effect of linking the two kinase activities increased phosphofructokinase activity results in elevated levels of fructose 1,6-bisphosphate, which activates pyruvate kinase. 

Phosphocreatine, glyceraldehyde-3-phos-phate dehydrogenase and, 48 Phosphofructokinase activity in adipose tissue, 47 glycolysis and, 49... 

Phosphofructokinase Activity in Various Yeasts Grown on D-Glucose... 

It was initially speculated that the antifungal action of organic acids is based on intracellular acidification, because this inhibits glycolysis (Leyva and Peinado, 2005). However, results obtained with exponentially growing cells, both in batch (Warth, 1991) as well as chemostat cultures (Verduyn et al., 1990), showed that glycolysis was enhanced when cells were cultured in the presence of sublethal concentrations of organic acids. It was also detected that phosphofructokinase activity was not inhibited (Warth, 1991). 

Citrate provides the precursors (acetyl-CoA, NADPH) for fatty acid synthesis and is a positive allosteric modulator of acetyl-CoA carboxylase, which is involved in the initiation of long-chain fatty acid synthesis (Chapter 18). It regulates glycolysis by negative modulation of 6-phosphofructokinase activity (see above). All of the above reactions occur in the cytoplasm, and citrate exits from mitochondria via the tricarboxylate carrier. 

Endogenous nitric oxide inhibits glucose-induced insulin secretion by suppression of phosphofructokinase activity in pancreatic islets. Biochem Biophys Res Commun 252 34-38. 

F-2,6-BE Thus, F-2,6-BP levels are decreased and phosphofructokinase activity is decreased. In liver and muscle, F-2,6-BP is the major allosteric activator of phosphofructokinase. In skeletal muscle, however, the kinase responsible for the synthesis of F-2,6-BP is activated, not inhibited, by cyclic AME Thus, muscle sees an increase in glycolysis following epinephrine stimulation, while the liver experiences a decrease in glycolytic activity. In both tissues, glycogen phosphorylase is activated and glycogenolysis occurs. Under these conditions, glucose is utilized in muscle for ATP production relative to contractile activity, while the liver produces glucose for export to the blood. 

Phosphofructokinase activity is sensitive to both positive and negative allosterism. For instance, when ATP is present in abundance, a signal that the body has sufficient energy, it binds to an effector binding site on phosphofructokinase. This inhibits the activity of the enzyme and, thus, slows the entire pathway. An abundance of AMP (adenosine monophosphate), which is a precursor of ATP, is evidence that the body needs to make ATP to have a sufficient energy supply. When AMP binds to an effector binding site on phosphofructokinase, enzyme activity is increased, speeding up the reaction and the entire pathway. 

Gilbert, H.F. (1982) Biological disulfides the third messenger Modulation of phosphofructokinase activity by thiol/disulfide exchange. 7. Biol. Chem. 257 12086-12091. 

Pollack, J.D. Williams, M.V. PPi-dependent phosphofructotransferase (phosphofructokinase) activity in the mollicutes (mycoplasma) Acholeplas-ma laidlawii. J. Bacteriol., 165, 53-60 (1986)... 

Betz, A. C. Moore. 1967. Ructuating metabolite levels in yeast cells and extracts, and the control of phosphofructokinase activity in vitro. Arch. Biochem. Biophys. 120 268-73. 

Frenkel, R. 1968. Control of reduced diphosphopyridine nucleotide oscillations in beef heart extracts. I. Effect of modifiers of phosphofructokinase activity. Arch. Biochem. Biophys. 125 151-6. 

Newtoa P. A. Hamer, M.J. (1989). Tissue-specific developmental changes in phosphofructokinase activity in embryonic and neonatal chick. Biochem. Soc. Trans., 17, 1106-7. 

Figure 8.1 Biochemical pathways involved in glucose catabolism in Pseudomonas putida KT2440. The metabolic network depicted is sketched around four main metabolic blocks, identified with different colors (i) the peripheral oxidative pathways, that encompass the oxidative transformation of glucose into gluconate and 2-ketogluconate (and the corresponding phosphorylated derivatives of these metabolites) (ii) the Embden-Meyerhof-Pamas (EMP) pathway (nonfunctional, due to the absence of a 6-phosphofructokinase activity) (iii) the...

Table 4.6 Percentage inhibition of phosphofructokinase activity by antimonials...

This enzyme catalyses one of the intermediate steps of glycolysis. The reaction is not considered to be a rate-lunitmg step, but it may be used as an indicator reaction for the estimation of phosphofructokinase activity which is thought to be rate limiting. Serum levels of aldolase are elevated in diseases of skeletal muscle and in the presence of tumours in many tissues. Aldolase may be assayed by an ultraviolet method using triose phosphate isomerase as an auxiliary reaction and glycerol-3-phosphate dehydrogenase as an indicator reaction [219]. The trioses can be trapped as formed with the aid of... 

---