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E Piatti

Publications and source records attributed to E Piatti.

At least 37 records · Page 2Linked to original sources
PubMed1990

Immunological studies on erythrocyte phosphoglucomutase isozymes.

Human erythrocytes (phenotype PGM1 a1 or PGM1 a3) contain two sets of phosphoglucomutase isozymes, produced by the expression of the PGM1 and and PGM2 loci. The two sets are constituted each by two forms, of which that called "secondary" is thought to derive from the post-translational modification of that called "primary". Cross-reactivities of these isozymes were studied by means of monospecific rabbit antibodies against purified human red cell PGM1 and PGM2 "primary" isozymes. The results show that the PGM1 and PGM2 forms are not immunologically related and provide further proof of the post-synthetic origin of "secondary" isozymes and of the multifunctionality of PGM2 phosphoglucomutases.

Antibodies↗
PubMed1989

Cell age dependent decay of human erythrocytes glucose-6-phosphate isomerase.

Glucose-6-phosphate isomerase shows a biphasic decay pattern during red blood cell aging, which is very fast during the first part of cell's life span in circulation. This decay is not due to accumulation of inactive enzyme molecules, as shown by immunological studies, but is accompanied by the formation of secondary isozymes (i.e., chemically modified forms). Electrophoretic and ion-exchange chromatographic experiments show that glucose-6-phosphate isomerase (D-glucose-6-phosphate ketol-isomerase, EC 5.3.1.9) consists of only one isozymic form in young erythrocytes but is present in two components, with different electric charge, in mature and old cells. This secondary isozyme is more stable to heat treatment and is inactivated by IgG anti-glucose-6-phosphate isomerase with a lower affinity than the native isozyme. In vitro incubation of homogeneous human glucose-6-phosphate isomerase under conditions known to produce enzyme deamination does not reproduce the isozymic pattern found in erythrocytes, suggesting that one or more mechanisms other than those previously described to explain glucose-6-phosphate isomerase microheterogeneity occur in the human erythrocyte.

Chromatography↗
PubMed1989

Isoenzymes of phosphoglucomutase from human red blood cells: isolation and kinetic properties.

A procedure has been developed for the purification of phosphoglucomutase from human red cell (phenotype PGM1 a1 or a3) lysates. It yields homogeneous isoenzyme preparations of the products ("primary" and "secondary") of the two PGM1 and PGM2 loci with distinctive pI (from 6.07 to 5.29). There are substantial differences between PGM1 and PGM2 isoenzymes, having single polypeptide chains of 58,500 and 69,000 Mr respectively and showing different thermostability. The kinetic properties of all the isoenzymes for the phosphoglucomutase reaction are essentially the same (apart from the specific activity of 1089-1263 units/mg for PGM1 forms vs 37-42 units/mg for PGM2 forms), but there are striking differences in substrate specificity. In fact the products of PGM1 locus are "true" phosphoglucomutases, being specific to mutate glucose monophosphates, whereas the PGM2 forms also display phosphoribomutase and glucose 1,6-bisphosphate synthetic activities. Some kinetic properties of these "side activities" are also reported.

Chromatography, DEAE-Cellulose↗
PubMed1986

Relationships between the age-dependent decay of glucose-1,6-bisphosphate synthesis, phosphoribomutase and phosphoglucomutase in human red cells.

In human red blood cells phosphoglucomutase exists in multiple molecular forms with different isoelectric points determined by two distinct loci called PGM1 and PGM2. With regard to the phosphoglucomutase PGM1 and PGM2 isoenzymes, the latter appear to be more important in erythrocyte metabolism owing to their ability to mutate ribose monophosphates and synthetize glucose-1,6-bisphosphate. In this paper we show that, beside undergoing age-related postranslational modifications, both phosphoglucomutase PGM1 and PGM2 forms decrease their activities as the mean cell age increases. Under the experimental conditions used to separate erythrocytes by age the comparison of the younger erythrocytes with the older shows that total phosphoglucomutase, phosphoribomutase and glucose-1,6-bisphosphate synthetic activities decay by 55%, 26% and 28%, respectively. We consider that these results substantiate the multifunctionality of PGM2 isoenzymes. Furthermore we discuss the role of these forms in the age-related decay of erythrocyte metabolism.

Aging↗
PubMed1985

Glucose-1,6-P2 synthesis, phosphoglucomutase and phosphoribomutase correlate with glucose-1,6-P2 concentration in mammals red blood cells.

Glucose 1,6-biphosphate (G1,6P2) was measured in human, pig, cow, rabbit, rat and sheep red blood cells. Mean values are variable among the species and range from 33 to 122 nmol/ml RBC for pig and rabbit erythrocytes, respectively. The activities of G1,6P2 synthase, phosphoglucomutase (PGM) and phosphoribomutase (PRM) have also been assayed in red cell haemolysates of the same species. The correlations between the biphosphate content and the occurrence of the three enzymatic activities have been studied in order to gain an insight into the regulation of the G1,6P2 turnover in mammalian erythrocytes.

Animals↗
PubMed1985

Glucose 1,6-bisphosphate decline in human erythrocytes: possible involvement of phosphoglucomutase PGM2 isoenzymes.

Human erythrocytes incubated with various sugars lower their glucose 1,6-bisphosphate (Glc-1,6-P2) content, as do haemolysates containing exogenous Glc-1,6-P2 incubated with sugar monophosphates (sugar-P). Experiments performed with isolated erythrocyte phosphoglucomutase (PGM) isoenzymes indicate that only definite isoenzymatic forms, namely PGM2, are able to consume Glc-1,6-P2 during the mutation of sugar-P other than glucose-P. In this process a phosphate group is released from Glc-1,6-P2 and can be partially recovered in the biphosphate of the mutated sugar-P. The relevance of this mechanism of Glc-1,6-P2 degradation is discussed in regard to the physiological turnover of the biphosphate.

Adenine Nucleotides↗
PubMed1984

[Degradative pathways of glucose 1,6-diphosphate in human erythrocytes].

In this study human erythrocytes have been incubated with various effectors most of which able to decrease the G1, 6P2 content. By using haemolysates and partially purified phosphoglucomutase isoenzymes we provide evidence that the G1, 6P2 decrease can be attributed to the ability of phosphoglucomutase PGM2 isoenzymes to mutate various sugar monophosphates. These isoenzymes, phosphorylated by G1, 6P2, may transfer the phosphate group to monophosphate sugars thus releasing the respective bisphosphate.

Adenine Nucleotides↗
PubMed1984

Acetaldehyde influences glucose 1,6-bisphosphate level of human erythrocytes in vitro and in vivo.

In intact erythrocytes from normal adults, acetaldehyde, besides inducing metabolite modifications otherwise observed, markedly decreases the glucose 1,6-bisphosphate (G1,6P2) level. Pyruvate rapidly reverses the acetaldehyde effects. Also in vivo, the acetaldehyde that occurs in the blood stream after heavy alcohol intake produces a significant decrease of the erythrocyte G1,6P2 concentration. These changes support the role of 1,3-bisphosphoglycerate as the first substrate in the G1,6P2 synthesis. The significance of the glucose bisphosphate as glycolytic modulator is also discussed.

Acetaldehyde↗
PubMed1983

Pig red blood cell hexokinase: regulatory characteristics and possible physiological role.

The regulatory properties of pig erythrocyte hexokinase III have been studied. Among mammalian erythrocyte hexokinases, the pig enzyme shows the highest affinity for glucose and a positive cooperative effect with nH = 1.5 at all the MgATP concentrations studied (for 0.5 to 5 mM). Glucose at high concentrations is also an inhibitor of hexokinase III. Similarly, the apparent affinity constant for MgATP is independent of glucose concentration. Uncomplexed ATP and Mg are both competitive inhibitors with respect to MgATP. Glucose 6-phosphate, known as a stronger inhibitor of all mammalian erythrocyte hexokinases, is a poor inhibitor for the pig enzyme (Ki = 120 microM). Furthermore, this inhibition is not relieved by orthophosphate as with other mammalian red blood cell hexokinases. A variety of red blood cell-phosphorylated compounds were tested and found to be inhibitors of pig hexokinase III. Of these, glucose 1,6-diphosphate and 2,3-diphosphoglycerate displayed inhibition constants in the range of their intracellular concentrations. In an attempt to investigate the role of hexokinase type III in pig erythrocytes some metabolic properties of this cell have been studied. The adult pig erythrocyte is able to utilize 0.27 mumol of glucose/h/ml red blood cells (RBC) compared with values of 0.56-2.85 mumol/h/ml RBC for the other mammalian species. This reduced capacity to metabolize glucose results from a relatively poor ability of the cell membrane to transport glucose. In fact, all the glycolytic enzymes were present and a low intracellular glucose concentration was measured (0.5 mM against a plasma level of 5 mM). Furthermore, transport and utilization were concentration-dependent processes. Inosine, proposed as the major energy substrate of the pig erythrocyte, at physiological concentrations is not as efficient as glucose in maintaining reduced glutathione levels under oxidative stress. Furthermore, newborn pig erythrocytes (fully permeable to glucose) possess hexokinase type II as the predominant glucose-phosphorylating activity. This fact and the information derived from the study of the regulatory characteristics of hexokinase III and from metabolic studies on intact pig erythrocytes permit the hypothesis that the presence of this peculiar hexokinase isozyme (type III) enables the adult pig erythrocyte to metabolize low but appreciable amounts of glucose.

Adenosine Triphosphate↗
PubMed1983

Red cell metabolism affects lactate and pyruvate partition across the plasma membrane.

The influence on red cell metabolism of increasing the glucose concentration or the pH of the medium has been examined in order to compare the modification of the lactate/pyruvate ratio inside and outside the cell. In both situations, we evidenced a constancy in the intracellular lactate/pyruvate ratio and an increase in the extracellular one, thus suggesting that the cell efficiently opposes cytoplasmic modifications. In fact an increase of lactate efflux takes place when the intracellular pyruvate decreases. The implications of these changes in the two compartments are discussed on the basis of the available results.

Cell Compartmentation↗
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↗
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↗
PubMedDate not supplied

The age-dependent metabolic decline of the red blood cell.

The oxidative and non-oxidative utilization of glucose was evaluated in human erythrocytes of different ages, separated by density gradient ultracentrifugation. Young red blood cells are able to metabolize 2.5 times more glucose than old ones; on the other hand, the amount of glucose utilized via the hexose monophosphate shunt does not show any age dependence. Glucose metabolism evaluated during in vivo ageing of a rabbit red cell population shows results very similar to those obtained for human cells. Metabolic stimulation of glucose utilization by high phosphate in both young and old human red cells increases glucose utilization by 40%. In the same way young and old erythrocytes were able to increase the amount of glucose metabolized via the hexose monophosphate shunt when an oxidative stimulus (methylene blue) was introduced. Human erythrocytes of different age possess similar abilities to transport glucose so that an age-dependent defect in glucose transport can be excluded. The ATP content of human and rabbit red blood cells, as a function of cell age, follows the decrease in glucose metabolized via the Embden-Meyerhof pathway. Reduced glutathione, on the other hand, after a small decrease associated with the "maturation" of reticulocytes into red cells, remains constant like the rate of the hexose monophosphate shunt.

Adenosine Triphosphate↗
PubMedDate not supplied

Human erythrocyte phosphoglucomutase: comparison of the kinetic properties of PGM1 and PGM2 isoenzymes.

Kinetic properties of PGM1 and PGM2 phosphoglucomutase "primary" isoenzymes from human erythrocytes were studied. The two enzyme forms share a "ping-pong" kinetic mechanism and show similar Km for substrate (glucose 1-P) and cofactor (glucose 1,6-P2). Micromolar concentrations of fructose 1,6-P2 and glycerate 2,3-P2 inhibit both PGM1 and PGM2 isoenzymes to a similar extent. The sole PGM2 form is affected by ribose monophosphates (ribose 1-P and ribose 5-P) that act as mutase inhibitors vs. glucose 1,6-P2 and as apparent activators vs. glucose 1-P. The interaction between PGM2 isoenzyme and ribose monophosphates is discussed in the light of the ability of this form to also display phosphoribomutase activity.

2,3-Diphosphoglycerate↗