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At least 865 records · Page 48Linked to original sources
PubMed1985

The effect of adenylate kinase activity on the rate and efficiency of energy transport from mitochondria to hexokinase.

The rate and efficiency of energy transport were examined in a system containing isolated rabbit heart mitochondria, hexokinase, adenylate kinase and low concentrations of adenine nucleotides. Oxygen consumption by mitochondria and glucose-6-phosphate synthesis by hexokinase were registered. It was found that when adenylate kinase is active both in mitochondria and in the environmental solution, the rate and efficiency (glucose-6-phosphate/O ratio) of glucose-6-phosphate formation considerably increase. The effects of adenylate kinase activity are fully abolished by diadenosine pentaphosphate, an inhibitor of adenylate kinase.

Adenine Nucleotides↗
PubMed1987

Hexokinase and adenylate kinase activities in aorta, heart muscle and skeletal muscle from uraemic rats.

The effect of parathyroidectomy and/or vitamin D on the development of arterial and myocardial lesions was studied in rats with moderate uraemia. The activities of hexokinase and adenylate kinase in the aorta, myocardium and skeletal muscle were measured and the incidence of aortic calcification and muscle cell necrosis determined. There was a decreased hexokinase activity in the aorta, myocardium and skeletal muscle from uraemic rats. Adenylate kinase showed an increased activity in the same tissues. Parathyroidectomy as well as I-alpha-hydroxycholecalciferol in a dose of 3 ng/100 g b.w. normalized these activities to a great extent. This effect did not occur when 10 ng/100 g b.w. was given. Parathyroidectomy in combination with a low dose of I-alpha-OH-D3 reduced the incidence of myocardial necrosis. Aortic calcifications were found in uraemic animals given 10 ng/100 g b.w. of I-alpha-hydroxycholecalciferol. In this group increased activity of adenylate kinase was found in calcified aortae but not in non-calcified aortae. The study shows that uraemia causes metabolic changes in the aorta, myocardium, and skeletal muscle which may partly be prevented by parathyroidectomy and by low doses of vitamin D. It also indicates some parallelism between these metabolic changes and the development of histologically demonstrable lesions in the aorta.

Adenylate Kinase↗
PubMed1988

Differential distribution of hexokinase in vital organs of three teleost fishes.

The phylogeny has influenced the distribution of hexokinase in various tissues of three teleosts, viz., Labeo rohita, Clarias batrachus and Channa punctatus, which differ significantly in a number of parameters like growth rate, feeding habits and ability to get oxygen. Among the organs investigated for hexokinase, the anterior region of the right lobe of the liver showed higher activity than the posterior region, followed by the anterior and posterior regions of the left lobe. The middle region of the renal tissue showed higher activity than the anterior or posterior region. In the muscle the caudal region showed maximum activity compared to the cephalic or thoracic regions. However, in g ills the enzyme concentration is higher in the left gill than in the right one. The observed variations are discussed in relation to the physiological status.

Animals↗
PubMed1979

Small angle X-ray scattering of dimeric yeast hexokinase in solution.

Small angle x-ray scattering measurements on dimeric yeast hexokinase B at pH 5.5 in acetate buffer yield a radius of gyration of 31.28 +/- 0.23 angstrom. This measured value is comparable to the radius of gyration of 31.5 angstrom calculated from the refined coordinates of the dimer in the BII crystal form. The hexokinase dimer found in the BI crystal form has a radius of gyration of 42 angstrom calculated from the atomic coordinates. Thus, the measured radius of gyration is consistent with the BII dimer being the predominant species in solution and rules out the existence of the BI dimer as a major species under these conditions.

Hexokinase↗
PubMedDate not supplied

Significance of serum phosphohexose isomerase, hexokinase and aldolase in carcinoma ovary.

The serum phosphohexose isomerase (PHI), aldolase and hexokinase activities have been determined in 36 patients of carcinoma ovary with different clinical stages and in 25 healthy normal female subjects. The serum PHI and hexokinase levels were significantly elevated (P less than .001) in all the stages of malignancy while serum aldolase was significantly elevated only in stages III and IV of malignancy. The enzyme levels showed statistically significant response to therapy in stage II patients. The mean values in patients with progression of the disease were not significantly different.

Female↗
PubMedDate not supplied

[Hexokinase and lactate dehydrogenase activity and isoenzymatic makeup of the soluble fraction of dissimilarly functioning rabbit muscles normally and in experimental allergic encephalomyelitis].

Only one isozyme of hexokinase (type I) was found in a soluble fraction of smooth muscle of rabbit stomach using column chromatography and polyacrylamide gel electrophoresis. By the pattern of metabolism the smooth muscle of rabbit stomach accupies an intermediate position between rapidly and slowly contracting sceletal muscles, approaching to musculus soleus by the activity and isozyme spectra of hexokinase and lactate dehydrogenase (LDH). Activity of these enzymes was altered not uniformly in dissimilarly functioning muscles of rabbits with experimental allergic encephalomyelitis: it was increased in musculus gastrocnemius of rabbits and decreased in soleus or in smooth muscles. LDH isoenzyme spectra changed towards an increase in aerobic H-subunits and decrease in anaerobic M-subunits in the soluble fraction of musculus gastrocnemius of rabbits with experimental allergic encephalomyelitis. Content of LDH-5 and LDH-4 was about 2-fold increased and content of LDH-1 and LDH-2 was decreased in musculus soleus.

Animals↗
PubMedDate not supplied

[Dynamics of erythrocyte hexokinase activity during glucose tolerance test in children with hereditary diabetes mellitus].

In determining the changes in hexokinase activity in erythrocytes during the glucose tolerance test in children with heredity aggravated by diabetes mellitus in comparison with such in apparently healthy children it was shown that in latent diabets the enzyme activity failed to alter during the whold period of study (on fasting stomach, 30, 60 and 180 minutes after glucose load), and increased 60 minutes after glucose load in potential diabetes, but to a lesser extent than in the control group. Changes of erythrocyte hexokinase response to glucose administration could serve as an auxiliary criterion for determination of the degree of risk in children with threatening diabetes.

Adolescent↗
PubMed1982

Regulation of glycolysis in Trypanosoma brucei: hexokinase and phosphofructokinase activity.

The kinetic properties of the glycosomal hexokinase (HG)2 and phosphofructokinase (PFK) from Trypanosoma brucei bloodstream forms were investigated. Hexokinase has a very high affinity for glucose (Km = 17 microM) and exhibits a broad pH optimum with a maximum at pH 7.8. No indications have been found for regulation of HK activity. Phosphofructokinase behaves as an allosteric protein with respect to its substrate, fructose-6-phosphate. 5'-AMP acts as a positive allosteric effector. The apparent Km for 5'-AMP is extremely low (7 microM). The other substrate for PFK is Mg2+-ATP chelate which activates the enzyme in a hyperbolic manner. Excess of ATP over Mg2+ is inhibitory. The enzyme needs Mg2+ for full activity. Compounds known to be positive or negative heterotrophic modifiers of PFK in other organisms are without effect. It is concluded that PFK and HK probably do not play a regulatory role in glycolysis in T. brucei.

Animals↗
PubMed1984

[Purification and properties of cytoplasmic and mitochondrial hexokinase from the rabbit brain].

The soluble Hexokinase from rabbit brain 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 properties of the purified cytoplasmic hexokinase were compared with those of the solubilized mitochondrial enzyme. No significant differences were found in M.W., pI and electrophoretic mobility. However, the temperature dependence of activity and specificity for several hexose substrates were markedly different.

Animals↗
PubMed1984

[Micromethods for the study of hexokinase in human erythrocytes].

A direct radioassay for the erythrocyte enzyme using U14C-glucose as substrate has been developed. With respect to the indirect spectrophotometric assay this method allows for the determination of true hexokinase activity. The assay proposed is sensitive, rapid and well suited for the determination of hexokinase activity in the erythrocyte lysate where the enzyme level is particularly low.

Erythrocytes↗
PubMed1984

[Hexokinase in bone marrow cells in the rabbit].

The hexokinase isozymic pattern of circulating reticulocytes fractionated by density gradient ultracentrifugation was studied. All the cellular fractions obtained show similar ratio of hexokinase Ia/hexokinase Ib while a four fold decay in specific activity was evidenced. Bone-marrow cells of anemic rabbits also contain low amounts of HK Ib while this isozymic form is not present in basophilic erythroblasts.

Anemia↗
PubMed1983

Red blood cell glucose metabolism in trisomy 10p: possible role of hexokinase in the erythrocyte.

Red blood cell glucose metabolism was investigated in a male patient with de novo trisomy 10p. According to previous evidence, when assigning hexokinase gene locus in the 10p11 leads to pter region, a triplex dosage effect of hexokinase activity (HK) was found, while all the other erythrocyte glycolytic enzymes were in the normal values range. Red blood cell glucose utilization was 2.87 mumole/hr/ml RBC as compared to 1.43 in normal controls; the rate of glucose metabolized through the hexose monophosphate shunt (HMPS) was unchanged. Glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate, and dihydroxyacetone phosphate increased with respect to normal controls, while normal levels of 3-phosphoglycerate, 2-phosphoglycerate, phosphoenolpyruvate, and ATP were found. The HK activity increased in all the red blood cell fractions obtained by density gradient ultracentrifugation. However, a small difference in the distribution of cells through the gradient was evident. The experiments reported in this article show that in the red blood cells of patients with trisomy 10p, an increased level of HK leads to higher concentrations of glucose-6-phosphate and to a faster glucose utilization in the Embden-Meyerhof pathway, while the HMPS rate is unchanged.

Blood Glucose↗
PubMed1983

Statistical comparison of blood glucose as determined by several test-strip procedures and by a hexokinase procedure.

We report a new statistical tool for comparing several dry-reagent strip procedures for whole blood glucose, which produce data in both digital and ordinal form, with results by the well-studied hexokinase-glucose-6-phosphate dehydrogenase procedure coupled to NAD+-NADH. Our use of "ordinal comparison unit" allows for a more equitable comparison of such data. These strip procedures produce biases of -2.21 to 1.74 ordinal comparison units over the range of glucose values corresponding to hypoglycemia and hyperglycemia, as compared with results by the hexokinase procedure, but they are essentially equivalent when compared with each other.

Blood Glucose↗
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↗
PubMed1978

Kidney in the aging cat: hexokinase, aldolase, L-alpha-glycerophosphate dehydrogenase, and lactate dehydrogenase histochemistry.

Hexokinase, aldolase, L-alpha-glycerophosphate dehydrogenase, and lactate dehydrogenase activities were determined in the kidney of the aging cat. Kidneys from 24 domestic cats 2 months to 7.5 years old in 6 age groups were examined by light microscopic and histochemical methods. Enzyme activities in anatomic components of the kidney were assessed on a quantitative basis for evaluation of mean activity between the age groups. In the cats with advancing age, renal components generally had stable activity. A significant (P less than 0.05) increase in hexokinase activity occurred with advancing age in the ascending part of the renal loop (Henle's loop) and in the distal convoluted tubule. Significant (P less than 0.05) increases in aldolase activity with aging were in cortical connective tissue, internal part of the glomerular capsule (podocytes), distal convoluted tubule, and convoluted segment (Pi) of the proximal portion of the nephron tubule. L-alpha-glycerophosphate dehydrogenase and lactate dehydrogenase activity increased significantly with aging in the convoluted (Pi) segment of the proximal portion of the nephron tubule.

Aging↗
PubMed1980

[Interactions of yeast hexokinase with ATP and AMP 4-(N-2-chloroethyl-N-methylamino)benzylamidates].

The interactions of ATP and AMP 4-(N-2-chloroethyl-N-methylamino)-benzylamidates with yeast hexokinase were studied. It was found that the ATP analog does not interact with hexokinase. The AMP analog irreversibly and almost completely inactivates hexokinse. A strong protective effect is exerted by MgATP. The value of apparent Ki for the AMP analog is equal to 2.10(4) M. The existence of affinity modification is postulated.

Adenosine Monophosphate↗
PubMedDate not supplied

[Effect of manganese on the sugar content, hexokinase and insulin activity of rabbit blood].

The paper deals with the effect of manganese on the sugar content and the hexokinase and insulin activity in the rabbit blood. The trace element in a dose of 0.1-3.0 mg/kg has a definite hypoglycemic effect. The sugar level lowers significantly during the whole period of the experiment with administration of 0.6 and 3.0 mg/kg of manganese; the activity of hexokinase and insulin being significantly increased. It is supposed that a change in the enzyme and insulin activity under the effect of manganese is one of the reasons of the sugar level decrease in the blood.

Animals↗
PubMed1978

D-Glucose anomeric preference of hexokinases in higher animals.

The D-glucose anomeric preference of hexokinases isolated from rat liver, brain, and skeletal muscle, and bovine retina was studied using the glucose-6-phosphate dehydrogenase-NADP system. The ratios of maximum phosphorylation rates of beta-D-glucose to those of alpha-D-glucose were 1.33, 1.46, and 1.54 for hexokinase types I, II, and III from rat liver, 1.45 and 1.63 for type I from rat brain and bovine retina, 1.53 for type II from rat skeletal muscle, and 0.55 (when determined at 5 mM) for type IV (glucokinase) from rat liver, respectively.

Animals↗