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At least 361 records · Page 20Linked to original sources
PubMed1986

Aspects on the phosphorylation of muscle phosphofructokinase by protein kinase C--inhibition by phosphofructokinase stabilisers.

Our report presents data on the phosphorylation of muscle phosphofructokinase by Ca2+-activated, phospholipid-dependent protein kinase. We have found a stoichiometrical phosphorylation (about 1.5 mol per mol subunit), and a low apparent Km (about 0.7 microM). These data speak in favor of a physiological role for the reaction, as does the fact that phosphofructokinase from a new species (rat) was successfully phosphorylated. On the other hand we present the hitherto unpublished circumstance that the phosphorylation is inhibited by conditions that stabilise the activity of phosphofructokinase. This fact makes us question the true significance of this reaction.

Adenosine Monophosphate↗
PubMed1987

beta-Galactosidase from rat epididymal fluid is bound by a recognition site attached to membranes of the epididymis different from the phosphomannosyl receptor.

In order to know if the beta-galactosidase of the rat epididymal fluid, as other secreted acid hydrolases, carries a marker in its molecule, we studied the binding of this enzyme to cellular membranes of the epididymal tissue. The binding, like that mediated by the phosphomannosyl receptor, was saturable, did not require calcium, had a Kd in the nM range and was inhibited by phosphatase or metaperiodate treatment of the enzyme. However fructose 6-phosphate derivates were more effective competitive inhibitors than mannose 6-phosphate. The binding capacity of the membranes were extractable with Triton X-100 and incorporable into liposomes. Trypsin inhibited the binding capacity of Triton extracts but it did not affect the affinity of intact cellular membranes for beta-galactosidase. The results suggest that a phosphorylated carbohydrate of the enzyme is bound by a recognizing site of the cellular membranes different from the phosphomannosyl receptor.

Animals↗
PubMed1987

Fluoride effects on 31P NMR spectra of macrophages.

31P High resolution nuclear magnetic resonance studies have been carried out on the P388D1 tumoral cell line and the BCG elicited alveolar rabbit macrophages both in sedimented cells and in perfused agarose-embedded cells. When the cells were sufficiently oxygenated, the phosphorylated sugars and ATP concentrations attained high levels. The intensity of the peak representing phosphorylated sugars varied inversely with ATP level when macrophagic cells were treated by NaF. The identities of the phosphorylated sugars were revealed by 1H and 31P NMR studies of the P 388D1 cells perchloric extracts.

Adenosine Triphosphate↗
PubMed1989

The site of substrate and fructose 2,6-bisphosphate binding to rabbit liver fructose-1,6-bisphosphatase.

The binding site(s) in rabbit liver fructose-1,6-bisphosphatase for the active site binding ligand, fructose 6-phosphate, and the inhibitor, fructose 2,6-bisphosphate, have been investigated by using nuclear magnetic resonance spectroscopy. The distance from a nitroxide spin label to the bound ligands and the distance from the structural metal site to the bound ligands are about the same within experimental error. These data indicate that the two ligands probably bind at the active site in the rabbit liver enzyme.

Animals↗
PubMed1990

A phospho-oligosaccharide can reproduce the stimulatory effect of insulin on glycolytic flux in human fibroblasts.

It has been recently demonstrated that insulin promotes the hydrolysis of a glycosyl-phosphatidylinositol, stimulating the release of a phospho-oligosaccharide which displays several insulin-like effects. In the present study we have investigated whether the compound is able to mimic insulin action on glucose metabolism in human fibroblasts. Similarly to the hormone, the phospho-oligosaccharide elicited a dose dependent increase in lactate output and fructose 2,6-bisphosphate content. The effect of the compound was time dependent with a progressive increase starting from 2 hours of incubation. 1 microM phospho-oligosaccharide had half maximal effect on both parameters, increasing glycolytic flux by approximately 30% and fructose 2,6-bisphosphate content by 70%. Therefore the phospho-oligosaccharide appears to be able to strictly reproduce insulin action on glucose metabolism in human fibroblasts.

Cells, Cultured↗
PubMed1992

Kinetics of phosphofructokinase from granulocytes isolated from patients with insulin resistance.

Phosphofructokinases from granulocytes isolated from insulin-resistant patients, mainly those from type II diabetics where the degree of insulin resistance was more pronounced, exhibit some changes in their kinetic behavior when assayed under allosteric conditions, characterized by an increased affinity for fructose-6-phosphate, being more resistant to ATP inhibition while it became more sensitive to citrate inhibitory effect. Those changes are suggestive of a isozymic modification to a more L-type enriched enzyme with a loss of the F-type component, probably present in the normal granulocyte.

Adenosine Triphosphate↗
PubMed1988

Glipentide and glucose metabolism in isolated rat hepatocytes.

Glipentide, a second generation sulfonylurea, raised the cellular concentration of fructose 2,6-bisphosphate in isolated rat hepatocytes. Parallel to accumulating this regulatory metabolite, glipentide inhibited basal gluconeogenesis and increased the rate of L-lactate production, as well as the metabolic flux through the 6-phosphofructo 1-kinase reaction. Tolbutamide elicited similar metabolic effects to those reported for glipentide, although the latter sulfonylurea was about 10 times more potent. The biochemical mechanism by which sulfonylureas promote the accumulation of fructose 2,6-bisphosphate in hepatocytes seems to be related to a significant increase of the hexose 6-phosphate pool (glucose 6-phosphate plus fructose 6-phosphate), together with the activation of 6-phosphofructo 2-kinase and inactivation of fructose 2,6-bisphosphatase, enzyme activities responsible, respectively, for the synthesis and degradation of fructose 2,6-bisphosphate.

Animals↗