Isozyme pattern in serially xenotransplanted childhood tumors.

Growth rate, histological course, and polymorphic enzyme pattern (glucose 6-phosphate dehydrogenase, glucose phosphate isomerase, and phosphofructokinase) were studied in eight childhood tumors xenotransplanted serially to nude mice. The growth rate of these tumors (three nephroblastomas, one hypercalcemic renal tumor, three rhabdomyosarcomas, and one malignant histiocytosis) appeared stable for any one particular tumor line. The time interval between two grafts varied from 1 to 3 weeks to 1 to 2 months in correlation with the clinical course of each malignant process. Histological changes were mostly in relation with a progressive dedifferentiation of the grafts. Immunoneutralization of glucose-6-phosphate dehydrogenase and glucose phosphate isomerase made possible the quantification of the stroma reaction in the grafts. A series of ten passages showed the amount of stroma to be constant for a given tumor type but variable from one tumor type to another, except for the malignant histiocytosis which showed an increase in stroma constituent after the sixth passage. One nephroblastoma tumor line showed, during the third passage, a sudden acceleration in the growth rate and complete transformation of the histological and isozymic patterns, which were interpreted as being the result of a murine lymphoma. The fibroblastic form of phosphofructokinase increased in every tumor line, whatever the tumor type. This change may be linked to a progressive dedifferentiation during the passage.

Purification and partial characterization of different forms of phosphofructokinase in man.

Phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) from human muscle, brain, heart and granulocytes has been purified using a two or three step purification procedure. The main step is Blue Dextran-Sepharose 4B chromatography with selective elution of phosphofructokinase by formation of the ternary complex ADP or ATP-fructose-6-P-enzyme. Muscle and heart contain only enzyme subunits with a molecular weight of 85,000. This type of subunit is predominnant in brain, where it co-exists with subunits of about 80,000 daltons. A single type of subunits is found in the granulocytes, with a molecular weight of 80,000. Anti-muscle phosphofructokinase antiserum reacts only with M-type enzyme. Anti-granulocyte enzyme antiserum, absorbed by pure brain phosphofructokinase, exhibits a narrow specificity against the so-called L-type enzyme. Anti-brain antiserum, absorbed by pure muscle phosphofructokinase and partly purified red cell enzyme, exhibits a narrow specificity against a phosphofructokinase form predominant in fibroblasts and present in brain (F-type).

Purification of F4 phosphofructokinase from human platelets and comparison with the other phosphofructokinase forms.

The phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) tetramers F4, F3L and F2L2 have been separated from human platelets, and purified to homogeneity by affinity chromatography on Dextran Blue-Sepharose 4B. The F subunits have a molecular weight of 85 000, identical to that of the M subunits. By contrast with L-type phosphofructokinase, the F-type enzyme seems to exist predominantly in a tetrameric form and not to aggregate to high molecular weight polymers. Specific activity of pure F4 phosphofructokinase is about 140 IU/mg of protein. Immunologically, it is easy to distinguish all the basic phosphofructokinase forms (i.e. M, L and F types); nevertheless a slight immunological cross-reactivity seems to exist between all these forms.

Endogenous phosphorylation of soluble enzymes in human red cells. Cyclic 3',5'-AMP-dependent phosphorylation of phosphofructokinase without detectable regulatory effect.

ATP-depleted human red cells have been incubated in a glucose-containing medium with [32P]orthophosphate in the presence and in the absence of cyclic 3',5'-AMP and dibutyril cyclic 3',5'-AMP. Spectrin, pyruvate kinase, phosphofructokinase, glucose-6-phosphate dehydrogenase and hemoglobin A1 have been purified and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Protein-bound radioactivity has been measured from the sodium dodecyl sulfate polyacrylamide gels and the trichloroacetic acid-precipitated proteins. In the cytosol, the most intense phosphorylation was found for pyruvate kinase whose, in the presence of cyclic AMP, specific radioactivity was comparable to that of the membrane protein and spectrin. In the absence of cyclic nucleotides it was five times less phosphorylated. Phosphofructokinase was only phosphorylated when the red cells were incubated with cyclic nucleotides; the extent of phosphorylation was four times less than for pyruvate kinase. Hemoglobin, glucose-6-phosphate dehydrogenase and a contaminant protein copurified with phosphofructokinase were not phosphorylated: the 'background' of the radioactivity found for these proteins was 100 times less than for pyruvate kinase and spectrin, and 20 times less than for phosphofructokinase (+cyclic AMP).

Hyperanodic forms of human glucose-6-phosphate dehydrogenase.

Pure glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49) is transformed into 'hyperanodic forms' when incubated at acidic pH and in the presence of NADP+ with excess of glucose-6-phosphate or with some 'NADP+ modifying proteins' purified from the same cells. The enzyme hyperanodic forms exhibit low isoelectric point, altered kinetic properties and high lability to heat, urea, and proteolysis. Differences between hyperanodic and native forms of glucose-6-phosphate dehydrogenase are also noted by microcomplement fixation analysis, ultraviolet absorbance difference spectrum and fluorescence emission spectrum. Drastic denaturation of the enzyme by urea and acid treatment did not suppress the difference of isoelectric point between native and hyperanodic forms of glucose-6-phosphate dehydrogenase. From our data we suggest that the conversion into hyperanodic forms could be due to the covalent binding on the enzyme of a degradation product of the pyridine nucleotide coenzyme. This modification could constitute a physiological transient step toward the definitive degradation of the enzyme.

Studies on the nature of different molecular forms of glucose-6-phosphate dehydrogenase purified from human leukocytes.

Several molecular forms of human glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49) corresponding to different stages of post-synthetic modifications have been purified from human leukocytes. The various enzyme forms were different in their specific activity, their kinetic properties and their isoelectrofusing pattern. The molecular weight of the subunits of the different forms was not modified. The changes in the electrofocusing pattern were not due to modifications of the N-terminal ends, the oxidation of thiol groups or the non-covalent fixation of an acid molecule upon the enzyme. Carboxypeptidase B cleaved a C-terminal lysine from the different enzyme forms and shifted the isoelectric point of the different enzyme active bands towards the acid pH. The different enzyme forms studied here seemed to result from the action upon 'native glucose-6-phosphate dehydrogenase' of 'modifying factors' especially abundant in some leukemic granulocytes. The modifying factors did not seem to be consumed during the 'modification' of glucose-6-phosphate dehydrogenase. Moreover, the storage for one year of unmodified enzyme resulted in changes in its electrofocusing pattern similar to those quickly induced by the 'modifying factors'. Consequently it appears that the modifying factors are catalysts of the modification of special residues of glucose-6-phosphate dehydrogenase. The hypothesis that this modification involves the deamination of asparagine or glutamine residues is put forward.

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.

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.

Human erythrocyte phosphoglycerate kinase deficiency: presence in a deficient patient of a stable variant with lowered catalytic activity.

The phosphoglycerate kinase deficiency found in one boy with hemolytic anemia was associated with an almost normal concentration of phosphoglycerate kinase-immunologically related material in the patient's erythrocytes. Consequently the catalytic activity of the mutant enzyme was drastically lowered. Besides, the abnormal phosphoglycerate kinase was more stable to heat and to urea than normal phosphoglycerate kinase and its isoelectric point was slightly increased.

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.

Mechanisms of the acquired erythrocyte enzyme deficiencies in blood diseases.

Acquired enzymatic activity defects of erythrocyte pyruvate kinase, glucose phosphate isomerase and phosphofructokinase have been studied in patients with acute myeloid leukemias, sideroblastic refractory anemias and unclassified acquired dyserythropoiesis. 6 patients with acute myeloid leukemia had a lowered erythrocyte pyruvate kinase activity; in 5 of them the concentration of the "pyruvate kinase"-antigen was parallely decreased, in such a manner that the ratio enzyme activity/immunologic reactivity (i.e. the molecular specific activity) was normal. In 1 patient with acute leukemia, 4 with refractory anemia and 1 with acquired dyserythropoiesis the defect of the pyruvate kinase activity was associated with a normal antigen concentration (and, therefore, the molecular specific activity in whole hemolysate was lowered). The enzyme activity was restored by incubation with SH reagents in two cases and by partial purification as often as it was performed. The electrofocusing pattern of erythrocyte pyruvate kinase was normal in both these types of defects. In two patients with so-called "acquired dyserythropoiesis" an erythrocyte glucose phosphate isomerase deficiency has been detected; in both the cases it was associated with a parallel decrease of the antigen concentration. The residual enzyme had a normal electrofocusing and electrophoretic pattern and a normal heat stability; the enzyme activity could not be restored by any treatment. In 1 patient with erythroleukemia and in 1 other with acquired dyserythropoiesis the erythrocyte phosphofructokinase activity was lowered. The enzyme activity was not restored by cross incubation in isologous plasma or by the SH reagents. In one case immunologic study could be performed, indicating that the enzyme defect was mainly due to the decreased ratio of the muscle type subunit of the erythrocyte phosphofructokinase. The electrofocusing pattern of deficient phosphofructokinases was normal. Finally, we point out the probable existence of several direct mechanisms, genetic and post translational, accounting for the acquired enzyme defects of red blood cells in various blood disorders.

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.

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.

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.

Phosphofructokinase in human fetus.

The isozymic composition of phosphofructokinase (EC.2.7.1.11) from human fetal tissues has been investigated by immunological characterization, electrophoresis, purification, and SDS-polyacrylamide gel electrophoresis of the dissociated subunits. One of the characteristics of fetal tissues is the indiscriminate expression by all the cells of two or three of the basic forms of phosphofructokinase without any isozyme really corresponding to a specifically fetal form. In particular, L-type enzyme, identical to the highly regulatory enzyme synthesized by the adult hepatocytes, is found in most fetal tissues, especially in muscle and brain. M-type subunits are also detected in most of the organs and constitute the major form in fetal muscle and adrenals. F-type subunits are predominant in fetal stomach and yolk sac and are practically the only form in fetal heart. Some electrophoretic and chromatographic differences between fetal and adult M-type phosphofructokinase exist; whether their nature is genetic or posttraductional is so far unknown. Some differences (of molecular weight and chromatographic properties) are also detected between the fetal L-type subunits and enzyme from adult granulocytes. A mild proteolytic attack of the former by subtilisin transforms it into an enzyme form indistinguishable from granulocyte phosphofructokinase.

G6PD deficiency with Gd(-)A like variant in a Chinese family from Cambodia.

A low rate value of G6PD was found in red blood cells from a Cambodian boy. Enzyme mapping was performed according to the WHO standard methods. G6PD presented all the characteristics of the A(-) variant encountered in the Negroes and behaved distinct from fast migrating enzymes described in China. No negro was in the ancestry of the mother.

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.