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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The changes are followed up in the properties of the macrophage membrane after treatment with phospholipase C and the activity of the glucose-6-phosphate dehydrogenase enzyme in order to elucidate the link between the conformation changes observed and some metabolic prosesses in antigen-stimulated macrophages. The studies were carried out on peritoneal macrophages of guinea pig-treated in vitro with phospholipase C. It was found that: 1. The action of phospholipase C essentially changes the linking parameters available for the fluorochrome 1-aniline-8-naphthalin sulfonic acid. 2. The activity of the glucose-6-phosphate dehydrogenase rises by 34.5% in the phospholipase C-treated macrophages. The fast changes observed in the conformation of the membrane that was studied under the effect of the fluorescence stain AHC, the higher activity of the dehydrogenase enzyme used after phospholipase C treatment, the fact that phospholipase C failed to pass through the macrophage membrane, and the capacity of the latter enzyme to bring about the same metabolic changes in the stimulation of the hexosomonophosphate cycle of the normal macrophages as well as the antigen stimulation produced made it reasonable to believe that the conformation changes produced a 'signal' that is transmitted through the cell membrane, and hence the metabolic changes that followed in the metabolic processes.
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PMID:[Relationship between membrane conformation changes and several metabolic processes in antigen-stimulated macrophages]. 72 42

Hepatic glucokinase is induced by insulin and repressed by glucagon. The effects of epidermal growth factor (EGF) on glucokinase expression were investigated in rat hepatocytes. EGF does not affect the decline in glucokinase activity in hepatocytes cultured for 48h in the absence of insulin, but it counteracts the increase in activity induced by insulin. This effect of EGF is greater in cells cultured at low cell density than in confluent cultures. EGF suppressed the insulin-induced increase in glucokinase mRNA levels by 50% indicating that its effect is at least in part at a pretranslational level. However, it potentiated the stimulatory effect of insulin on glucose-6-phosphate dehydrogenase activity and mRNA, indicating that the effect on glucokinase expression is due to a specific post-receptor mechanism. The effect of EGF on glucokinase mRNA expression is mimicked by phospholipase D but not by phosphatidylinositol-specific phospholipase C or by phorbol ester, an activator of protein kinase C, suggesting that it is unlikely to be mediated by activation of protein kinase C.
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PMID:Epidermal growth factor counteracts insulin-induced expression of glucokinase in hepatocytes. 800 30

The efflux of lactate dehydrogenase and haemoglobin from human erythrocytes during prolonged incubation at 37 degrees was significantly reduced by ATP, ADP, AMP, UTP, creatine phosphate, or phosphoenolpyruvate and to a lesser extent by fructose, glucose 6-phosphate or fructose 6-phosphate, but not by glucose. Iodoacetate, however, markedly increased the loss of haemoglobin and slightly increased that of lactate dehydrogenase. Phospholipase C greatly accelerated the relase of haemoglobin, lactate dehydrogenase, pyruvate kinase, hexokinase, glucose 6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase from human erythrocytes, but this effect was also reduced in the presence of ATP or ADP. The loss of lactate dehydrogenase, malate dehydrogenase, and pyruvate kinase from the cells treated with phospholipase C increased as their ATP content fell. In a series of experiments in which the action of phospholipase C was stopped by the subsequent addition of trypsin, ATP and ADP (1 mmol/l) significantly reduced the efflux of haemoglobin, but AMP had no such effect. The results are consistent with the conclusion from our previous work that enzyme leakage is related to diminution in the energy content of the cells. The protective action of AMP on cells not treated with phospholipase C, however, differs from earlier findings with rat lymphocytes and it is suggested that in red cells it might be converted into ATP or that it has a direct effect on the permeability of the cell membrane.
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PMID:Factors affecting the release of haemoglobin and enzymes from human erythrocytes. 1563 25