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M Dachà

Publications and source records attributed to M Dachà.

At least 55 records · Page 3Linked to original sources
PubMed1982

Multiple forms of human red blood cell hexokinase. Preparation, characterization, and age dependence.

Human red blood cell hexokinase (EC 2.7.1.1) has been shown to exist in multiple molecular forms which are separable by ion exchange chromatography. Of the major forms, designated hexokinase Ia, Ib, and Ic, only hexokinase Ia corresponds to hexokinase type I from human liver, while the others differ from every other previously reported hexokinase isozyme. Hexokinase Ib is the predominant form in the fetal erythrocytes, while it is present at lower levels in the red blood cells of adults. Analysis of the hexokinase isozymic pattern in red cells of different mean age shows that the level of hexokinase Ib is also dependent on the age of the cell. The three major forms of hexokinase have the same molecular weight of 100,000, by sedimentation velocity on sucrose density gradients, the same Michaelis constants, substrate and coenzyme specificity, pH-dependent activity, and the same thermal stability. The only significant differences were found in the isoelectric points which were 5.7 pH units for hexokinase Ia, 5.5 pH units for hexokinase Ib, and 5.35 pH units for hexokinase Ic. These data, together with that previously reported for rabbit erythrocytes (Stocchi, V., Magnani, M., Canestrari, F., Dachà, M., and Fornaini, G. (1981) J. Biol. Chem. 256, 7856-7861) suggest that the presence of multiple forms of hexokinase is a common phenomenon in mammalian red blood cells.

Adult↗
PubMed1982

A new variant of galactokinase.

A new variant of human galactokinase activity is described. This enzyme shows reduced catalytic activity both in red and white blood cells, lower Km for ATPMg2-, and increased in vivo instability when compared to the normal enzyme. Thermostability and pH optimum are not modified. We have labelled this enzyme the Urbino variant and have suggested the procedure to distinguish it from the allelic form (GALKG) responsible for galactosemia in the homozygous state.

Alleles↗
PubMed1981

Rabbit red blood cell hexokinase. Evidence for two distinct forms, and their purification and characterization from reticulocytes.

Rabbit hexokinase (EC 2.7.1.1) has been shown to exist in the soluble fraction of reticulocytes as two distinct molecular forms, designated hexokinase Ia and hexokinase Ib, which are separable by ion exchange chromatography and polyacrylamide gel electrophoresis. Hexokinase Ia was found to be similar to the brain enzyme, while hexokinase Ib differs from every other previously reported hexokinase isozyme. Reticulocyte hexokinase Ia and Ib have been purified 55,000-and 50,000-fold, respectively, by a combination of ion exchange chromatography, affinity chromatography, and preparative polyacrylamide gel electrophoresis, as proteins homogeneous by sodium dodecyl sulfate-gel electrophoresis. The native proteins have the same molecular weight of 105,000 by gel filtration and sedimentation velocity on sucrose density gradients. Sodium dodecyl sulfate-polyacrylamide gels have a molecular weight of 104,000, indicating that the two forms are monomers. Hexokinase Ia had a pI of 6.2 to 6.3 pH units while hexokinase Ib had a pI of 5.7 to 5.8 pH units by isoelectric focusing. The two enzymes were specific for Mg.ATP and Mg.ITP as the nucleotide substrates. Several hexoses could be phosphorylated by hexokinase Ia and Ib with different affinities.

Animals↗
PubMed1981

Glucose utilization in human erythrocytes during physical exercise.

Red blood cells obtained from well-trained athletes consumed glucose at a higher rate than those from sedentary subjects when incubated in vitro in a glucose containing medium at 37 degrees C. Similar results were obtained when fructose was substituted for glucose, but not when galactose was the monosaccharide. The utilization of glucose by erythrocytes can occur both via the Embden-Meyerhof and Pentose phosphate pathways (PPP). In the present experiments, there were no differences in the activities of select enzymes in these pathways or in metabolic intermediates of the erythrocytes. An exception was an elevated 2,3-diphosphoglycerate (2,3DPG) in the erythrocytes of the athletes. Additional experiments are needed to identify changes in the red blood cells of the athletes which produce the increased consumption of glucose.

Adolescent↗
PubMed1980

Action of oxidized and reduced glutathione on rabbit red blood cell hexokinase.

Reduced glutathione at 1 mM concentration is able to mantain rabbit red blood cell hexokinase (EC 2.7.1.1) in the reduced state with fully catalytic activity. At higher concentrations a marked inhibition is observed. In contrast, oxidized glutathione is a strong inhibitor of reduced erythrocyte hexokinase at all the concentration studied. Inactivation experiments show that some sulfhydryl groups reacting with oxidized glutathione are responsible for the enzyme inactivations. These findings suggest a cellular inter-relationship between redox and energetic metabolism coupled through glutathione at the hexokinase level.

Adenosine Triphosphate↗
PubMed1980

Rabbit red blood cell hexokinase. Purification and properties.

Rabbit red blood cell hexokinase (EC 2.7.1.1.) has been purified 300,000-fold by a combination of ion exchange chromatography, affinity chromatography, and preparative polyacrylamide gel electrophoresis. The hexokinase activity has been isolated in 35% yield as a protein that is homogeneous by polyacrylamide and sodium dodecyl sulfate gel electrophoresis. The highest specific activity obtained was 145 units/mg of proteins. The native protein has a molecular weight of 110,000 by gel filtration on Ultrogel AcA 44 and 112,000 by sedimentation velocity on sucrose density gradients. Sodium dodecyl sulfate-polyacrylamide gels gave a molecular weight of 110,000 indicating that hexokinase is a monomer. The enzyme had a pI of 6.20 to 6.30 pH units by isoelectric focusing. The enzyme was specific for Mg . ATP and Mg . ITP as the nucleotide substrates. Several hexokinase with different affinities.

Adenosine Triphosphate↗
PubMed1980

Modification of the hexokinase activity in the red blood cells of subjects with differentiated adenocarcinoma.

In the present work we found a significant increase of erythrocyte HK activity in subjects suffering from differentiated adenocarcinoma. Some erythrocyte enzymatic activities (such as HK, PK, G-6-PD, 6-PGD, PHI and GR) in the red blood cells of 96 subjects, of which 55 were healthy or with noncancerous pathology and 41 had malignant tumors, are considered. Evident modification was shown only for the HK, which together with PFK and PK are limiting steps of glycolysis.

Adenocarcinoma↗
PubMed1979

Decay pattern of rabbit erythrocyte hexokinase in cell aging.

As previously reported, during rabbit red blood cell aging glucose phosphorylating activities show several modifications. In the first period of the red cell life span the predominant form is similar to hexokinase II, while in the mature erythrocyte the predominant glucose phosphorylating activity resembles hexokinase I. In the oldest cells glucose phosphorylating activity has a low affinity (high Km) for glucose. In this paper the modifications of hexokinase in cell aging have been studied in vivo in a young erythrocyte population synchronized by actinomycin D, and in vitro in red cells separated in fractions according to different ages. Since protein synthesis is lacking in the mature red cell, we are inclined to explain the presence of low-affinity hexokinase activity in the oldest erythrocytes as an age-dependent transformation of a primary hexokinase.

Animals↗
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↗
PubMed1978

Comparative studies on red blood cell glucose phosphorylating activities of mammals.

1. ATP-D-hexose-6-phosphotransferase activity was measured in red blood cells of man, rabbit, pig and cow. Mean values ranged from 0.60 to 1.06 units/g haemoglobin and no significant difference was obtained with different glucose concentrations. 2. The characteristics of glucose phosphorylating activities in red blood cells of the species studied were similar. 3. Chromatography on DEAE column revealed two different glucose phosphorylating activities in red cells of man, rabbit and pig, and only one in cow red cells. 4. The first hexokinase activity is the predominant form and is saturated with low glucose concentrations; the second is noticeably marked at high glucose concentrations.

Animals↗
PubMed1978

Glucokinase and hexokinase in pig erythrocytes.

We have shown different enzymatic activities responsible for the phosphorylation of glucose in pig erythrocytes. These activities were observed after partial purification from hemolyzed red cells. One of the enzymes involved is the hexokinase which is present in all tissues; the other is similar to hepatic glucokinase. We have determined the kinetic properties of these activities in hemolysates and in partially purified preparations. Their electrophoretic-migration characteristics were studied too.

Animals↗
PubMed1977

Inherited erythrocyte pyruvate kinase deficiency: Studies on 15 members of two related families.

The case of a haemolytic non-spherocytic anaemia with pyruvate kinase (PK) deficiency is reported. The investigation concerns two families with a low level of PK. In the propositus and in the members of his family we have also examined the behaviour of some enzymes and the concentration of red cell metabolites. We confirm the heterogeneity of the manifestation and agree that anaemias due to PK deficiency are complex forms in which the enzyme defect is only one of the symptoms.

Anemia, Hemolytic, Congenital Nonspherocytic↗