Phosphofructokinase activity

About: Phosphofructokinase activity is a research topic. Over the lifetime, 485 publications have been published within this topic receiving 15082 citations.

Muscle fiber composition in patients with traumatic cord lesion.

Abstract: Muscle fiber composition and oxidative and glycolytic enzymatic activity have been studied with complete traumatic transection of the spinal cord and spastic paralysis of the lower extremities. Muscle sample were taken by means of needle biopsy from the vastus lateralis, gastrocnemius, and soleus muscles. Biopsies were also taken for comparison from the deltoid muscle. Fibers staining darkly for alkaline stable myofibrillar ATP-ase (type II) dominated or were the only fibers identified in the paralysed muscles. The deltoid muscles of the same patients had a rather even mixture of type I and II fibers. Staining pattern was reversed after acid preincubation (pH 4.3). Mean diameters in the paralysed muscles were reduced for both fiber types. All fibers stained relatively weakly for NADH-diaphorase. Succinyldehydrogenase activity was low and phosphofructokinase activity usually moderately reduced. The findings imply that neuronal influence on the muscular fibers had led to a change in the staining characteristics of the muscle fibers. Such a change migh indicate altered contractile characteristics, though the detailed nature of the observed findings in still unclear.

Phosphorus-31 nuclear magnetic resonance studies of wild-type and glycolytic pathway mutants of Saccharomyces cerevisiae.

Abstract: High-resolution phosphorus-31 nuclear magnetic resonance (31P NMR) spectra of wild-type and mutant strains of Saccharomyces cerevisiae were observed at a frequency of 145.7 MHz. Levels of various phosphorus metabolites were investigated upon addition of glucose under both aerobic and anaerobic conditions. Three mutant strains were isolated and their biochemical defects characterized: pfk lacked phosphofructokinase activity; pgi lacked phosphoglucose isomerase activity; and cif had no glucose catabolite repression of the fructose bisphosphatase activity. Each mutant strain was found to accumulate characteristic sugar phosphates when glucose was added to the cell suspension. In the case of the phosphofructokinase deficient mutant, the appearance of a pentose shunt metabolite was observed. 31P NMR peak assignments were made by a pH titration of the acid extract of the cells. Separate signals for terminal, penultimate, and central phosphorus atoms in intracellular polyphosphates allowed the estimation of their average molecular weight. Signals for glycero(3)phosphochline, glycero(3)phosphoserine, and glycero(3) phosphoethanolamine as well as three types of nucleotide diphosphate sugars could be observed. The intracellular pH in resting and anaerobic cells was in the range 6.5--6.8 and the level of adenosine 5'-triphosphate (ATP) low. Upon introduction of oxygen, the ATP level increased considerably and the intracellular pH reached a value of pH 7.2--7.3, irrespective of the external medium pH, indicating active proton transport in these cells. A new peak representing the inorganic phosphate of one of the cellular organelles, whose pH differed from the cytoplasmic pH, could be detected under appropriate conditions.

Early Changes in Energy Metabolism in the Myocardium Following Acute Coronary Artery Occlusion in Anesthetized Dogs

Abstract: The tissue content of energy-rich phosphates and glycolytic metabolites and the activity of myocardial enzymes were examined in the dog after producing myocardial infarction by ligating branches of the anterior descending and circumflex coronary arteries. The pattern of systolic fiber movement shown by a strain-gauge assembly differentiated ischemic from nonischemic portions of myocardium. In ischemic muscle, 30 minutes after onset of ischemia, creatine phosphate content fell from 8.0 to 1.4 µmoles/g, ATP content fell from 5.8 to 1.5 µmoles/g, lactate content rose tenfold, and α-glycerophosphate content rose fivefold. The content of energy-rich phosphates and glycolytic metabolites did not change much in nonischemic muscle. The activities of myocardial enzymes were assayed in extracts of tissue samples from ischemic and nonischemic muscle 5 to 120 minutes after coronary artery occlusion. The activities of aldolase, lactic dehydrogenase (LDH), glyceraldehydephosphate dehydrogenase, α-glycerophosphate dehydrogenase, malate dehydrogenase (MDH), and 6-phosphogluconate dehydrogenase did not change significantly in ischemic muscle during 2 hours of observation. In nonischemic muscle, phosphofructokinase activity increased 75% 5 minutes after coronary occlusion, followed by an increase in activity of isocitrate dehydrogenase, creatinephosphokinase, MDH, and LDH. The enzymatic changes in nonischemic muscle suggest metabolic changes in nonischemic muscle accompanying compensatory hyperfunction and increased energy requirements of surviving muscle.

Activity of the plasma membrane H(+)-ATPase and optimal glycolytic flux are required for rapid adaptation and growth of Saccharomyces cerevisiae in the presence of the weak-acid preservative sorbic acid.

Abstract: The weak acid sorbic acid transiently inhibited the growth of Saccharomyces cerevisiae in media at low pH. During a lag period, the length of which depended on the severity of this weak-acid stress, yeast cells appeared to adapt to this stress, eventually recovering and growing normally. This adaptation to weak-acid stress was not due to metabolism and removal of the sorbic acid. A pma1-205 mutant, with about half the normal membrane H+-ATPase activity, was shown to be more sensitive to sorbic acid than its parent. Sorbic acid appeared to stimulate plasma membrane H+-ATPase activity in both PMA1 and pma1-205. Consistent with this, cellular ATP levels showed drastic reductions, the extent of which depended on the severity of weak-acid stress. The weak acid did not appear to affect the synthesis of ATP because CO2 production and O2 consumption were not affected significantly in PMA1 and pma1-205 cells. However, a glycolytic mutant, with about one-third the normal pyruvate kinase and phosphofructokinase activity and hence a reduced capacity to generate ATP, was more sensitive to sorbic acid than its isogenic parent. These data are consistent with the idea that adaptation by yeast cells to sorbic acid is dependent on (i) the restoration of internal pH via the export of protons by the membrane H+-ATPase in an energy-demanding process and (ii) the generation of sufficient ATP to drive this process and still allow growth.