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Biomedical subjects

V Stocchi

Publications and source records attributed to V Stocchi.

133 records · Page 8Linked to original sources
PubMed1978

Relationship between glucose phosphorylating activities and erythrocyte age.

Glucose phosphorylating activity of human erythrocytes quickly decreases during cell ageing; the electrophoretic pattern suggests that this fast decrease is due mainly to the isozyme II. We have shown that in the young cells only hexokinase I and II are responsible for the glucose phosphorylation, while in the old cells another glucose phosphorylating activity, more evident at high glucose concentration, is also present. The appearance of this activity during cell ageing could be interpreted as a post-translational modification of the native hexokinase.

Erythrocytes↗
PubMedDate not supplied

Quantitation of electrophoretic eluted proteins.

Quantitation of stained, electroeluted proteins by the classical Lowry and Bradford protein assay is not possible because of some different interferences. In particular we have found that the substance interfering in the Lowry method cannot be removed by trichloroacetic acid precipitation nor can be compensated for by the appropriate blank. Interferences in the Bradford protein assay are due to detergents and pH of the protein buffer as well as to Coomassie brilliant blue R250 electroeluted with the protein sample. However, while these interferences can be compensated for by appropriate blank and standard curves, others (probably due to acrylamide fines) cannot be corrected. All these problems can be overcome by concentration and dialysis of electroeluted samples which permit the removal of interfering substances and the use of Bradford and Lowry protein assay in the 1-20 micrograms range, respectively. Successful applications are described for electroeluted bovine serum albumin, human hexokinase and phosphoglucomutase.

Animals↗
PubMedDate not supplied

Role of hexokinase in the regulation of glucose metabolism in human erythrocytes.

Red blood cell glucose metabolism was studied in erythrocytes from a patient with trisomy 10 p which resulted in + 50% hexokinase specific activity, in normal controls and in cases of heterozygous hexokinase deficiency. The results obtained show that the hexokinase activity level is an important factor in the control of the erythrocyte's glycolytic rate while having no appreciable effect on the hexose monophosphate pathway under resting conditions. No clear conclusion could be drawn when an oxidative stress was present.

Blood Glucose↗
PubMedDate not supplied

Purification and properties of the cytoplasmic hexokinase from rabbit brain.

About 90% of the total hexokinase activity in rabbit brain was found to be associated with mitochondria while the remaining part was found in the cytosolic fraction. The soluble enzyme was purified 4,700-fold to near homogeneity by a combination of ion-exchange chromatography, dye-ligand chromatography and affinity chromatography. The purified enzyme showed a specific activity of 110 units/mg of protein and was obtained in 70% yield. The molecular weight of the purified hexokinase was found to be approximately 98,000 both for the native and the denatured enzyme. The isoelectric point, pI, was 6.2 pH units by isoelectric focusing and the enzyme was found to be able to phosphorylate several hexoses. Mg . ATP2-, among the nucleotide substrates, was the most effective phosphate donor. The properties of the purified cytoplasmatic hexokinase were compared with those of the solubilized mitochondrial enzyme. No significant differences were found in molecular weight, isoelectric point, pH dependence of activity, electrophoretic mobility and affinity for glucose and Mg.ATP2-. However, the temperature dependence of activity, and the specificity for several hexose substrates were markedly different.

Animals↗
PubMedDate not supplied

Effects of buffers and pH on rabbit red blood cell hexokinase.

The kinetic properties of rabbit red blood cell hexokinase in different buffer systems have been studied. At pH 8.0 the reaction velocity (v) is about 30% higher in glycylglycine compared to Tris, Tea, Hepes or ammonium acetate buffers. The enzyme stability, heat-dependence and spectral properties of the enzyme are also affected by the buffer utilized. None of the following kinetic properties of red blood cell hexokinase varies with pH in the range 6.8-8.5: Km of glucose; Km of ATP and Ki of glucose 6-phosphate.

Acetates↗
PubMedDate not supplied

Action of orthophosphate on rabbit red blood cell hexokinase.

1. Orthophosphate (Pi) at low concentrations, is able to activate the glucose 6-phosphate, glucose-1,6-diphosphate or 2,3-diphosphoglycerate-inhibited hexokinase (E.C. 2.7.1.1). In contrast, at high concentrations it is competitive inhibitor of MgATP2- with a Ki of 20 mM. 2. The Pi effect on inhibited hexokinase is pH dependent and becomes lower as the pH increase. The similar pH-dependence of the Ki of glucose-1,6-diphosphate with the pH-independence of the Ki of glucose 6-phosphate here reported, suggest the coincidence of the C-1 phosphate, of glucose-1,6-diphosphate and Pi binding sites. 3. Activation of uninhibited hexokinase by Pi at pH lower than the physiological ones has been demonstrated to be an artefact.

Adenosine Triphosphate↗