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Biomedical subjects

K Uyeda

Publications and source records attributed to K Uyeda.

At least 91 records · Page 5Linked to original sources
PubMed1980

An activation factor of liver phosphofructokinase.

Pure phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) from liver is strongly inhibited by ATP, whereas crude phosphofructokinase is only slightly inhibited by ATP. A factor that is removed from the enzyme during purification and can prevent the inhibition of phosphofructokinase by ATP has been isolated. The factor can be resolved into three components that differ in molecular weights, as shown by gel filtration on Sephadex G-25. These factors overcome the ATP inhibition but have no effect on the catalytic activity under the optimum assay conditions. Furthermore, AMP acts syngeristically with the activation factor in reversing ATP inhibition. It is proposed that the activation of phosphofructokinase by the activation factor and AMP is sufficient to account for the glycolytic flux in the liver.

Adenosine Triphosphate↗
PubMed1979

Hormone-stimulated phosphorylation of liver phosphofructokinase in vivo.

The effect of glucagon on the phosphorylation and the enzymic activity of phosphofructokinase in rat liver in vivo was investigated. Glucagon stimulated the phosphorylation of liver phosphofructokinase approximately 3- to 5-fold and increased cAMP levels 5-fold and blood glucose levels 2-fold over the values obtained for control animals. The specific radioactivity of ATP isolated from liver was the same in both control and hormone-treated animals. During the purification of the 32P-labeled enzyme from both animals, no difference was observed in the total or specific enzyme activities of the enzymes from the various fractions. Thus, phosphofructokinase appears to be phosphorylated in vivo by a cyclic AMP-dependent protein kinase. Although phosphorylation does not affect the maximum catalytic activity of the enzyme, it does render the enzyme significantly more sensitive to ATP inhibition. Thus, at a given concentration of ATP, the phosphorylated phosphofructokinase exhibits considerably lower activity than the unphosphorylated enzyme. The possible relationship between our observations and glucagon-mediated control of glycolysis is discussed.

Adenosine Triphosphate↗
PubMed1979

Phosphofructokinase.

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Allosteric Regulation↗
PubMed1977

Changes in allosteric properties of phosphofructokinase bound to erythrocyte membranes.

Human and rabbit erythrocyte membranes prepared by hypotonic hemolysis contained 5 to 15% of the phosphofructokinase in the erythrocytes. The membrane-bound phosphofructokinase can be eluted by a saline wash. Human erythrocyte and rabbit muscle phosphofructokinase bind to the saline-washed membranes. This binding is specific for the inner surface of the membrane. The amount of phosphofructokinase bound is dependent on pH; at pH 7, 6 times more enzyme is bound than at pH 7.5. Unlike free phosphofructokinase, the membrane-bound phosphofructokinase is not inhibited by ATP or 2,3-diphosphoglycerate, and its fructose-6-P saturation curve is nonsigmoidal.

Adenosine Triphosphate↗
PubMed1977

Erythrocyte adenosine triphosphate and 2,3-diphosphoglycerate after human renal transplantation: dissociation from hypophosphataemia.

1. Erythrocyte 2,3-diphosphoglycerate (2,3-DPG) and adenosine triphosphate (ATP) were determined in normal individuals, uraemic patients on chronic haemodialysis and patients who underwent renal transplantation, and correlated with plasma phosphate and arterial blood pH. 2. Significant increases in the 2,3-DPG and ATP content were found in the uraemic patients and these persisted after transplantation in spite of marked hypophosphataemia. 3. No correlation was established with plasma phosphate for either of the compounds but 2,3-DPG had a significant correlation with arterial blood pH. 4. Normal values for ATP and 2,3-DPG were observed in post-transplant patients with normal haematological values. The high amounts of erythrocyte 2,3-DPG and ATP in the early post-transplant period are independent of the circulating concentration of inorganic phosphate, and might represent the response of erythrocyte glycolysis to changing arterial blood pH.

Adenosine Triphosphate↗
PubMed1977

Electron microscopic observations on the lesions of herpes zoster with topical application of interferon.

The lesions of herpes zoster in three patients were investigated electron microscopically before and after topical application of interferon. In the blister, on the 5th to 7th day after its formation, the following were seen: acantholytic cells with virus particles in the nucleus and cytoplasm, multinucleated cells derived from keratinocytes, edematous and degenerated keratinocytes containing virus particles and tonofibrillar materials, macrophages with many large vacuoles, neutrophils, lymphocytes and Langerhans's cells. After the first application of interferon, the findings for keratinocytes were the same as those of before application and keratinocytes were frequently found adjacent to macrophages. The macrophages were large and had numerons large vacuoles in the cytoplasm. After the second application of interferon, virus particles were often seen in the vacuoles of the macrophages in comparison with that before application. In the cytoplasm of macrophages, acantholytic keratinocytes and tonofibrillar materials were phagocytized. Many virus particles were seen in the vacuoles of some acantholytic keratinocytes. It was concluded from these findings that the macrophages accelerated the phagocytotic activity of the virus particles.

Administration, Topical↗
PubMed1976

Studies on the fatty acid inactivation of phosphofructokinase.

Investigation of phosphofructokinase in normal and regenerating livers led to the discovery of an inactivating factor in the extracts of these livers. The inactivating factor was found to be a mixture of free fatty acids. The fatty acid compositions of the normal and regenerating livers are the same, but the concentrations of most of the fatty acids are at least 3 to 4 times higher in the latter. Inactivation of phosphofructokinase by palmitate and oleate was investigated using purified rabbit muscle enzyme. Incubation of the enzyme with palmitate (250 muM) or oleate (50 muM) resulted in rapid inactivation of the enzyme with biphasic curves. The concentrations of oleate and palmitate required to produce 50% inactivation of the enzyme were 35 muM and 75 muM, respectively. Fructose-6-P (0.5 mM), MgATP, (1 mM), fructose-1,6-P2 (1 mM), AMP (1 mM), and cyclic adenosine 3':5'-monophosphate (20 muM) protected the enzyme against inactivation when these metabolites were incubated with the enzyme before the addition of fatty acid. Bovine serum albumin (100 muM) and beta-cyclodextrin (0.25 mM) also protected the enzyme against the inactivation. However, if the enzyme was inactivated by fatty acid, subsequent addition of the above metabolites or bovine serum albumin did not reactivate the enzyme. Binding studies with [3H]oleate revealed at least three types of binding sites. The first site binds 2 to 4 mol of oleate/mol of enzyme. Oleate binding to this site did not seem to affect the enzyme activity. The second binding site binds 5 to 15 mol of oleate/mol of enzyme resulting in complete loss of the activity. This is followed by an increase in oleate binding to the third site of the enzyme. Sucrose density gradient centrifugation of oleate-inactivated enzyme indicated that the enzyme dissociated to the dimeric form. Similarly, centrifugation of [3H]oleate-treated enzyme revealed that all polymeric forms of phosphofructokinase bound approximately 6 to 8 mol of oleate/mol of enzyme. In the presence of fructose-6-P, oleate is bound to the polymers to a lesser degree and therefore protects against the fatty acid inactivation. Various polymers which are cross-linked with dimethylsuberimidate are also inhibited by oleate.

Adenosine Monophosphate↗