scholarly journals Glucose 6-phosphate activation of pyruvate kinase from Mycobacterium smegmatis

1981 ◽  
Vol 193 (2) ◽  
pp. 435-440 ◽  
Author(s):  
R Kapoor ◽  
T A Venkitasubramanian
Keyword(s):  
Pyruvate Kinase ◽  
Mycobacterium Smegmatis ◽  
Kinase Activity ◽  
Hill Coefficient ◽  
Saturation Curve ◽  
Pyruvate Kinase Activity ◽  
Physiological Conditions ◽  
Sigmoidal Kinetics ◽  
High Degree ◽  
Variable Substrate

1. Activation of glucose 6-phosphate is one of the unique properties of pyruvate kinase from Mycobacterium smegmatis. 2. Pyruvate kinase, partially purified from ultrasonic extracts of the mycobacteria by (NH4)2SO4 fractionation, exhibited sigmoidal kinetics at various concentrations of phosphoenolpyruvate, with a high degree of co-operativity (Hill coefficient, h = 3.7) and S0.5 value of 1.0 mM. 3. In the presence of glucose 6-phosphate, the degree of co-operativity shown by the phosphoenolpyruvate saturation curve was decreased to h = 2.33 and the S0.5 value was lowered to 0.47 mM. 4. The enzyme was activated by AMP and ribose 5-phosphate also, but the activation constant was lowest with glucose 6-phosphate (0.24 mM). 5. The enzyme was strongly inhibited by ATP at all phosphoenolpyruvate concentrations. The concentrations of ATP required to produce half-maximal inhibition of enzyme activity at non-saturating (0.2 mM) and saturating (2 mM) phosphoenolpyruvate concentrations were 1.1 mM and 3 mM respectively. 6. The inhibition of ATP was partially relieved by glucose 6-phosphate. 7. The enzyme exhibited Michaelis-Menten kinetics with ADP as the variable substrate, with an apparent Km of 0.66 mM. 8. The enzyme required Mg2+ or Mn2+ ions for activity. It was not activated by univalent cations. 9. The kinetic data indicate that under physiological conditions glucose 6-phosphate probably plays a significant role in the regulation of pyruvate kinase activity.

scholarly journals Regulation of rat liver pyruvate kinase. The effect of preincubation, pH, copper ions, fructose 1,6-diphosphate and dietary changes on enzyme activity

1968 ◽  
Vol 108 (3) ◽  
pp. 427-436 ◽  
Author(s):  
E. Bailey ◽  
F. Stirpe ◽  
C B Taylor
Keyword(s):  
Pyruvate Kinase ◽  
Rat Liver ◽  
Kinase Activity ◽  
Copper Ions ◽  
Maximal Activity ◽  
Pyruvate Kinase Activity ◽  
Significant Reversal ◽  
Sigmoidal Kinetics ◽  
Influence Of Ph ◽  
Allosteric Activator

1. Preincubation of partially purified rat liver L-type pyruvate kinase at 25° for 10min. causes a marked increase in co-operativity with respect to both the substrate, phosphoenolpyruvate, and the allosteric activator, fructose 1,6-diphosphate. 2. The results are consistent with the existence of two forms of liver L-type pyruvate kinase, designated forms LA and LB. It is postulated that form LA has a low Km for phosphoenolpyruvate (about 0·1mm) and is not allosterically activated, whereas form LB is allosterically activated by fructose 1,6-diphosphate, exhibiting in the absence of the activator sigmoidal kinetics with half-maximal activity at about 1mm-phosphoenolpyruvate. In the presence of fructose 1,6-diphosphate, form LB gives Michaelis–Menten kinetics with Km less than 0·1mm. It is further postulated that preincubation converts form LA into form LB. 3. The influence of pH on the preincubation effect was studied. 4. The inhibition of pyruvate kinase by Cu2+ was studied in detail. Though phosphoenolpyruvate and fructose 1,6-diphosphate readily protect the enzyme against Cu2+ inhibition, little evidence of significant reversal of the inhibition by these compounds could be found. 5. The effects of starvation, fructose feeding and preincubation on the pyruvate kinase activity of crude homogenates of various tissues of the rat were also studied.

Red blood cell age, pyruvate kinase activity, and insulin receptors. Evidence that monocytes and RBCs may behave differently

Diabetes ◽  
1983 ◽  
Vol 32 (11) ◽  
pp. 1017-1022 ◽  
Author(s):  
A. Camagna ◽  
R. De Pirro ◽  
L. Tardella ◽  
L. Rossetti ◽  
R. Lauro ◽  
...  
Keyword(s):  
Blood Cell ◽  
Pyruvate Kinase ◽  
Red Blood Cell ◽  
Kinase Activity ◽  
Insulin Receptors ◽  
Pyruvate Kinase Activity ◽  
Cell Age

Red Blood Cell Age, Pyruvate Kinase Activity, and Insulin Receptors: Evidence that Monocytes and RBCs May Behave Differently

Diabetes ◽  
1983 ◽  
Vol 32 (11) ◽  
pp. 1017-1022 ◽  
Author(s):  
A. Camagna ◽  
R. D. Pirro ◽  
L. Tardella ◽  
L. Rossetti ◽  
R. Lauro ◽  
...  
Keyword(s):  
Blood Cell ◽  
Pyruvate Kinase ◽  
Red Blood Cell ◽  
Kinase Activity ◽  
Insulin Receptors ◽  
Pyruvate Kinase Activity ◽  
Cell Age

scholarly journals Kinetic studies on the regulation of rabbit liver pyruvate kinase

1973 ◽  
Vol 131 (2) ◽  
pp. 287-301 ◽  
Author(s):  
M. G. Irving ◽  
J. F. Williams
Keyword(s):  
Pyruvate Kinase ◽  
Specific Activity ◽  
Deae Cellulose ◽  
Kinetic Studies ◽  
Rabbit Liver ◽  
Hill Coefficient ◽  
Saturation Curve ◽  
Low Concentrations ◽  
Ammonium Sulphate Fractionation ◽  
The Hill

Two kinetically distinct forms of pyruvate kinase (EC 2.7.1.40) were isolated from rabbit liver by using differential ammonium sulphate fractionation. The L or liver form, which is allosterically activated by fructose 1,6-diphosphate, was partially purified by DEAE-cellulose chromatography to give a maximum specific activity of 20 units/mg. The L form was allosterically activated by K+ and optimum activity was recorded with 30mm-K+, 4mm-MgADP-, with a MgADP-/ADP2- ratio of 50:1, but inhibition occurred with K+ concentrations in excess of 60mm. No inhibition occurred with either ATP or GTP when excess of Mg2+ was added to counteract chelation by these ligands. Alanine (2.5mm) caused 50% inhibition at low concentrations of phosphoenolpyruvate (0.15mm). The homotropic effector, phosphoenolpyruvate, exhibited a complex allosteric pattern (nH+2.5), and negative co-operative interactions were observed in the presence of low concentrations of this substrate. The degree of this co-operative interaction was pH-dependent, with the Hill coefficient increasing from 1.1 to 3.2 as the pH was raised from 6.5 to 8.0. Fructose 1,6-diphosphate interfered with the activation by univalent ions, markedly decreased the apparent Km for phosphoenolpyruvate from 1.2mm to 0.2mm, and transformed the phosphoenolpyruvate saturation curve into a hyperbola. Concentrations of fructose 1,6-diphosphate in excess of 0.5mm inhibited this stimulated reaction. The M or muscle-type form of the enzyme was not activated by fructose 1,6-diphosphate and gave a maximum specific activity of 0.3 unit/mg. A Michaelis–Menten response was obtained when phosphoenolpyruvate was the variable substrate (Km+0.125mm), and this form was inhibited by ATP, as well as alanine, even in the presence of excess of Mg2+.

Pyruvate kinase activity in cerebral hemispheres and cerebellum-brainstem of normal and hypoxic-ischemic newborn rats

2004 ◽  
Vol 3 (3) ◽  
pp. 152-155 ◽  
Author(s):  
Hacer Yapicioglu ◽  
Mehmet Satar ◽  
Nejat Narli ◽  
Levent Kayrin ◽  
Ercan Tutak
Keyword(s):  
Pyruvate Kinase ◽  
Kinase Activity ◽  
Cerebral Hemispheres ◽  
Newborn Rats ◽  
Pyruvate Kinase Activity

Superoxide dismutase and cytochrome oxidase in collapsed lungs: possible role in reexpansion edema

1988 ◽  
Vol 65 (1) ◽  
pp. 235-241 ◽  
Author(s):  
R. M. Jackson ◽  
A. L. Brannen ◽  
C. F. Veal ◽  
J. D. Fulmer
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome Oxidase ◽  
Pyruvate Kinase ◽  
Kinase Activity ◽  
H2o2 Production ◽  
Lung Collapse ◽  
Pyruvate Kinase Activity ◽  
Sod Activity ◽  
Control Rabbit ◽  
Radical Production

This study examined the effects of lung collapse, a condition that causes relative hypoxia in lung tissues, on superoxide dismutase (SOD), cytochrome oxidase (cyt ox), and pyruvate kinase (py ki) activities in rabbits. Cyanide-insensitive respiration measurements were done in collapsed and contralateral lungs, as an index of intracellular free radical production. Rabbits' right lungs were collapsed for 7 days after which the animals were killed. We found that control rabbit lungs contained approximately 25 SOD units/mg DNA measured with 10(-5) M KCN (total SOD) and approximately 11 SOD units/mg DNA measured with 10(-3) M KCN (mitochondrial or MnSOD). Right lung collapse caused a 25% decrease in mitochondrial SOD activity after 7 days (P less than 0.05), whereas no significant changes occurred in right or left lungs' total SOD activity. In control rabbits cyt ox activity averaged approximately 0.009 mumol ferrocytochrome c.min-1.mg DNA-1. Right lung collapse caused a greater than 40% decrease in cyt ox activity after 7 days of collapse (P less than 0.05), whereas cyt ox activity in contralateral left lungs did not change. Pyruvate kinase activity, a marker for anaerobic glycolysis resulting from tissue hypoxia, increased 49% in collapsed right lungs (P less than 0.01). Cyanide-insensitive respiration was 83% higher in 7 day-collapsed lungs (2.28 +/- 0.66 microliters O2.min-1.g-1) compared with contralateral lungs (1.24 +/- 0.34, P less than 0.05), indicating increased O2-. and H2O2 production in this tissue after homogenization at normoxic PO2 (approximately 150 Torr).(ABSTRACT TRUNCATED AT 250 WORDS)

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