Biomedical subjects

D Cottreau

Publications and source records attributed to D Cottreau.

28 records · Page 2Linked to original sources

PubMed1976

Glucose-phosphate isomerase deficiency due to a new variant (GP I Barcelona) and to a silent gene: biochemical, immunological and genetic studies.

A 12-year-old girl of Spanish origin was found to be double heterozygote for a deficient GP I variant (GP I Barcelona) and for a silent GP I gene. The mother was heterozygote for GP I Barcelona and the father was heterozygote for the silent gene. GP I Barcelona was a fast variant (116%) with an increased isoelectric point (9.55), lability to heat and to urea, and shift of the pH curve towards the acidic pH. The other kinetic characteristics were normal. The ratio of enzymatic activity to immunological reactivity was normal in erythrocytes and white blood cells of the father and the mother but decreased to 75% of normal in blood cells of the daughter. The genetic and molecular mechanisms of GP I deficiency of this patient are discussed.

Adult↗

PubMed1976

Human leukocyte glucose-phosphate-isomerase purification by affinity elution and immunological study.

The authors have purified glucose phosphate isomerase (GPI) from human leukocytes ; they used as starting material leukemic leukocytes obtained from a patient with hyper-leukocytic acute myeloid leukemia ; it was possible to obtain several milligrams of pure enzyme from a single patient. The purification procedure includes a two step precipitation by ammonium sulfate and one column chromatography on a cation exchanger with specific elution by 6 phosphogluconate, a ligand of GPI ; of the two cation exchangers tested, phosphocellulose was found to lead to a better yield than CM-Sephadex. The end product of purification had a specific activity of 855 UI/mg and gave only one band in sodium dodecyl sulphate polyacrylamide gel electrophoresis. Anti GPI monospecific rabbit serum was obtained with purified enzyme. GPI from the various blood cells of ten normal controls was studied immunologically and the ratio of the enzymatic activity to the immunological reactivity was measured ; this ratio (i.e. the molecular specific activity) was lower in granulocytes than in lymphocytes and still more depressed in platelets and hemolysate. The significance of such differences is discussed.

Blood Platelets↗

PubMed1976

Modifications of purified glucose-6-phosphate dehydrogenase and other enzymes by a factor of low molecular weight abundant in some leukemic cells.

Highly purified platelet glucose-6-phosphate dehydrogenase (G6PD; D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49) can be modified in its isoelectric point and its molecular specific activity by extracts of some leukemic granulocytes. The "G6PD modifying factors" are relatively small molecules (molecular weight slightly under 5000), thermostable, dialyzable, and ultrafilterable. These molecules are destroyed by various endo- and exopeptidases and by serine enzymes present in crude extracts of leukocytes and commercial preparations of ribonuclease. The alterations of platelet G6PD due to the "G6PD modifying factors" are stable and not reversible by dialysis or further chromatography. The leukemic extracts which are able to modify G6PD also can modify the electrophoretic mobility and (or) the enzymatic activity of purified leukocyte pyruvate kinase, 6-phosphogluconate dehydrogenase, and glucosephosphate isomerase. The chemical nature of such modifications and their relationships with post-translational modifications which occur in leukemic or normal cells are discussed.

Blood Platelets↗

PubMed1976

Human platelet glucose-6-phosphate dehydrogenase. Total purification, kinetic studies and relationship with enzyme from other blood cells.

Human platelet G-6-PD has been highly purified, to homogeneity, and its kinetic, electrophoretic and immunological characteristics have been studied. Platelet G-6-PD differs from erythrocyte or leukocyte enzymes by an increased Michaelis constant for G-6-P and a slow activity at the acid pHs. By electrofocusing only a main active band (band a) of platelet G-6-PD was found. The incubation at 37 degrees C in the presence of NADP+ and dithiothreitol normalize Km-G-6-P of platelet G-6-PD; the incubation with boiled and ultrafiltered leukemic granulocyte extracts led to an anodisation of G-6-PD active forms, a decrease of the molecular specific activity and a further increase of Km-G-6-P; these last modifications are the same as those undergone by G-6-PD incubated in crude extracts of normal or leukemic granulocytes.

Blood Platelets↗

PubMed1976

Human granulocyte phosphoglycerate kinase. Purification by double affinity elution and immunological study.

Human phosphoglycerate kinase has been totally purified from leukemic granulocytes by double 'affinity elution' with ATP and 3-phosphoglycerate. This purification procedure allowed to obtain 19 mg of protein, specific activity of which was 400 IU/mg i.e. a 105-fold purification and an overall yield of 47%. Purified enzyme was homogenous when tested by acrylamide sodium dodecyl sulfate electrophoresis and immunodiffusion. Specific antibodies raised in rabbits totally inactivated phosphoglycerate kinase of crude extracts as well as of the purified preparation. The molecular specific activity (i.e. the ratio enzyme activity/immunological reactivity) was identical in leukocytes, platelets, erythrocytes and was identical in these cells to the value found for the totally purified phosphoglycerate kinase.

Antigen-Antibody Reactions↗

PubMed1976

Causal mechanisms of multiple acquired red cell enzyme defects in a patient with acquired dyserythropoiesis.

A patient with an unclassified form of acquired dyserythropoiesis was found to have multiple defects in erythrocyte enzyme activity, involving especially pyruvate kinase (PK), glucose phosphate isomerase (GPI), and phosphofructokinase (PFK). The PK activity defect was associated with a normal concentration of PK-related antigen, and the enzyme could be reactivated during the procedure of partial purification of the enzyme. The concentration of GPI-related antigen was as reduced as the GPI enzymatic activity, and the defect was not improved by any treatment (cross-incubation of red cells or treatment of the hemolysate by SH reagents); the residual enzyme had a normal stability to heat, and a normal electrophoretic and electrofocusing pattern. The PFK activity defect was not improved either by cross-incubation of red cells or by treatment with SH reagents. Immunologic data with antimuscle and antileukocyte antisera seemed to indicate that the defect involved especially the muscle-type subunit of erythrocyte PFK. In agreement with this assumption was the fact that deficient PFK was markedly more inhibited by ATP than normal enzyme. Changes similar to those of deficient PFK herein studied were noted for PFK of unfractionated erythrocytes from premature newborns or of "old" erythrocytes from full-term infants. It appeared that each of the three enzyme defects detected in the patient could be due to a different mechanism, involving post-translational changes, decreased synthesis, and possible reversion of the genetic regulation mechanisms of the abnormal erythroid precursors toward a fetal type. The possible relationships between these various phenomena and the nature of a hypothetical common underlying cause are discussed.

Anemia, Hemolytic, Congenital Nonspherocytic↗

PubMed1975

Gd(--) Abrami: a deficient G-6PD variant with hemizygous expression in blood cells of a woman with primary myelofibrosis.

A new deficient G-6PD variant, Gd(--) Abrami, was found in granulocytes, platelets and red blood cells of a 65-year-old woman with myelofibrosis. Enzyme and immunological titrations showed that only the deficient variant was present in blood cells whereas both the normal and abnormal enzymes were found in the fat cells of this patient. These results seem to indicate that the granulocytes, platelets and erythrocytes of this woman with myelofibrosis have arisen from a single abnormal precursor the functional X chromosome of which is the one carrying the abnormal G-6PD gene.

Adipose Tissue↗

PubMed1975

Gd(minus)Matam, an African glucose-6-phosphate dehydrogenase variant with enzyme deficiency. Biochemical and immunological properties in various hemopoietic tissues.

Two unrelated Senegalese patients, both native of the Matam province, were found to have the same deficient G6PD variant. One has no hematological history, the other had several induced acute hemolytic episodes. The deficiency was almost complete in red blood cells and 20-30 percent of the normal level in leukocytes and platelets; in leukocytes the deficiency was due to a decrease in the molecular specific activity of the enzyme to which a molecular instability was added, explaining the greater deficiency in red blood cells. The electrophoretic mobility was slightly fast in leukocytes and platelets but normal in red blood cells. This pattern was confirmed by electrofocusing in ampholine-acrylamide gel. From a kinetic point of view, these enzymes were characterized by a lowered Km (G6P) (13 to 20 muM) a normal Km (NADP+), a Ki (NADPH) increased about twice, a thermal instability, a biphasic pH curve and an increased activation energy (15 kcal/mole). The polymorphonuclear cells were functionally strictly normal: engulfment, nitroblue tetrazolium (NBT) reduction test, induced iodination, and oxygen consumption were normal. The authors discuss the importance of post-synthetic modifications of the muted enzymes and their repercussions on the enzyme characteristics.

Blood Platelets↗

PubMed1975

Human granulocyte 6 phosphogluconate dehydrogenase. Purification by elective elution with NADP+, immunological and kinetic properties.

Human granulocyte 6 phosphogluconate dehydrogenase has been totally purified from a single patient with chronic granulocytic leukaemia. 48 mg of protein, of specific activity 20 IU per mg of protein, have been obtained in the course of three different steps only. The overall yield was 30 p. cent and the purification was 100 folds. Purified 6 phosphogluconate dehydrogenase was homogeneous when tested in acrylamide and acrylamide SDS gel electrophoresis or in immunodiffusion. The enzyme was immunologically identical in red blood cells, blood platelets and normal leukocytes. The fixation of both substrates, NADP-+ and 6 phosphogluconate, seemed to proceed through a non ordered mechanism. NADPH was an inhibitor strictly competitive with respect to NADP-+ and non competitive with respect to 6 phosphogluconate. 2-3 Diphosphoglycerate seemed to be able to bind on both the fixation sites of NADP-+ and 6 phosphogluconate. The inhibition by ATP was competitive with 6 phosphogluconate and non competitive with NADP-+. 6 phosphogluconate dehydrogenase was inactivated by SH reagents and was partially protected against this inactivation by both substrates. Both substrates protected the enzyme against thermal inactivation. The influence of ionic strength, pH and ions have been studied, and the results have been compared to those reported by other authors for erythrocyte enzyme.

Adenosine Triphosphate↗

PubMed1975

Post translational modifications of glucose-6-phosphate dehydrogenase in human leukemias.

The modifications of the electrofocusing pattern, the immunological reactivity and the kinetic properties of glucose 6 phosphate dehydrogenase have been studied in malignant blood cells of various leukemias and myeloproliferative disorders. 1. Granulocytic G-6PD forms with decreased isoelectric points have been found in all the acute myeloid leukemias and erythroleukemias, and in most of the chronic granulocytic leukemias and myelofibrosis. In contrast, granulocytic G-6PD from patients with polycythemia vera always was normal. On the same way leukemic lymphocyte or lymphoblast G-6PD was identical to that from normal lymphocytes. 2. The ratio of enzymatic activity to immunological reactivity (=molecular specific activity) was markedly decreased in the myeloblasts of two patients with acute myeloid leukemia, and in the erythroblast-rich cellular fraction of a patient with erythroleukemia. In these cells the decrease of molecular specific activity was parallel to the alteration of the electrofocusing pattern of G-6PD. 3. The enzymatic forms with decreased isoelectric point also exhibited an altered affinity for glucose 6 phosphate. These modifications are post translational alterations of the neosynthesized G-6PD, since this enzyme is a single molecule, coded by the same gene in all tissues; they seem to correspond to an accelerated molecular aging due to an increased concentration of "G-6PD modifying factors". The significance of such an increased concentration of these G-6PD modifying factors in malignant cells is discussed.

Glucosephosphate Dehydrogenase↗