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G Jacobasch

Publications and source records attributed to G Jacobasch.

At least 37 records · Page 2Linked to original sources
PubMed1991

[Diagnosis of genetically determined diseases].

Enzymopathies of pyruvate kinase are caused by defects of structural genes forming stable and unstable mutants, respectively. Stable mutants of PK are characterized by high S0,5 PEP and nearly unchanged Vmax. A decrease of PEP affinity can be the result from a very high allosteric constant L0 or from an increased KPEP. From the pattern of PAGE can be concluded that stable PK mutants are tetraheteromers composed of two normal and two shortened polypeptide chains. We suppose that this is the result of a mutation of a codon which stops the polypeptide synthesis of PK earlier. Most PK mutants are unstable. They are characterized by low catalytic activity and high PEP affinity. The kinetic properties of unstable mutants are changed posttranslational by proteolytic modifications. Furthermore low S0,5 PEP values result from a persistence of the isoenzyme PK-K in reticulocytes and erythrocytes, respectively. A prenatal diagnosis of PK enzymopathies can be carried out with a very small blood volume by using the method of isoelectrophoretic focussing.

Chromatography, Affinity↗
PubMed1990

Phosphofructokinase from Plasmodium berghei. Influence of Mg2+, ATP and Mg2(+)-complexed ATP.

The control enzyme phosphofructokinase is of regulatory significance in the metabolism of glucose by the malarial parasite Plasmodium berghei. (1) The enzyme was partially purified from erythrocytic stages of P. berghei by precipitation with poly(ethylene glycol) and chromatography on 2',5'-bisphosphoadenosine-Sepharose 4B. (2) Similarly to various other phosphofructokinases, the enzyme from P. berghei shows an allosteric behaviour. It is activated by fructose 6-phosphate and inhibited by ATP. (3) The effects of Mg2(+)-complexed ATP, free ATP and Mg2+ were studied by keeping constant the concentration of one of these and varying the concentrations of the other two. (4) The enzyme is shown to be allosterically inhibited by free ATP and by higher concentrations of Mg2+. Compared with phosphofructokinase of erythrocytes, inhibition by ATP is weaker by two orders of magnitude. Mg2(+)-complexed ATP has no effect on allosteric regulation. (5) The proposed kinetic model provides an adequate description of the data.

Adenosine Triphosphate↗
PubMed1990

Microheterogeneity of human erythrocyte pyruvate kinase: application of immunological visualization techniques after isoelectric focusing in ultrathin gels.

Immunological methods for protein visualization afford high sensitivity, good specificity and resolution. We used the indirect immunoassay with peroxidase- and 125I-labelled antibodies to investigate the microheterogeneity of pyruvate kinase from human red blood cells and can show an enzyme pattern with more than 10 single bands. Different methods were tested as to their applicability for protein fixation and subsequent immunological visualization in polyacrylamide gels. Besides the Western blot, immunofixation and ethanolic fixation can be recommended as fixation techniques, especially after isoelectric focusing in ultrathin gels.

Acrylic Resins↗
PubMed1990

Glucose-6-phosphate dehydrogenase from Plasmodium berghei: kinetic and electrophoretic characterization.

Evidence is given for the existence of a parasite-specific glucose-6-phosphate dehydrogenase (G6PD) in Plasmodium berghei by characterization of its kinetic and electrophoretic properties. From infected rat erythrocytes the parasites were isolated, washed, and lysed. G6PD was purified by affinity chromatography with 2'5'-ADP-Sepharose 4B, although the separation of the malaria-specific enzyme from that of the host cell was not complete. Malarial G6PD significantly differed from the red cell enzyme with respect to its electrophoretic properties. In cellulose acetate electrophoresis, a band with catodic mobility was observed in addition to the anodically mobile host cell enzyme at pH 7.0. The subunits of the parasite-specific G6PD have a molecular weight of 55 kDa in contrast to 59 kDa of red cell G6PD subunits. The enzyme from P. berghei shows no cross-reactivity with polyclonal antibodies against G6PD from rat erythrocytes. Thus, a close evolutionary relationship between both proteins and the presence of proteolytic modifications could be excluded. The Km value for G6P of malarial G6PD is increased by one order of magnitude compared with the host cell enzyme.

Animals↗
PubMed1990

Phosphofructokinase from Plasmodium berghei: a kinetic model of allosteric regulation.

As in mammalian cells, phosphofructokinase (PFK) is of major regulatory importance in the glucose metabolism of Plasmodium berghei. The malarial enzyme shows allosteric properties similar to PFK from various sources; it is activated by fructose-6-phosphate and inhibited by ATP, but differs with respect to allosteric regulation. Enzyme activity is only marginally increased by AMP, a potent activator of many phosphofructokinases. Phosphoenolpyruvate, which is reported to inhibit PFK activity, efficiency activates the malarial enzyme. No activation by ADP was observed. Instead, ADP inhibits the enzyme non-allosterically and competitively to the substrate MgATP. Phosphate stimulates the catalytic activity of malarial PFK independently of the activation by F6P and PEP.

Adenosine Diphosphate↗
PubMed1990

Mathematical modelling of metabolic pathways affected by an enzyme deficiency.

The regulation of metabolic pathways of the red cell affected by an enzyme deficiency is studied on the basis of comprehensive mathematical models. The main steps of such a theoretical approach are outlined considering individual alterations in the kinetic properties of two regulatory enzymes: pyruvate kinase and glucose-6-phosphate dehydrogenase. It is demonstrated that mathematical modelling helps to relate the observed changes of cellular quantities as shortened life-span, or as resistance against oxidative stress to alterations in the metabolic regulation.

Animals↗
PubMed1990

Regulation of the energy metabolism of Plasmodium berghei.

Energy metabolism of malaria parasites was investigated in P. berghei infected red blood cells of rat. Although Plasmodia contain mitochondria most of their ATP is formed by glycolysis. Lactate formation is two orders of magnitude higher than in noninfected erythrocytes. The coupling of respiration and glycolysis is very loose, a Pasteur-effect was not found. The key enzymes of glycolysis hexokinase and phosphofructokinase have been partially purified and kinetically characterized. The kinetic properties of both enzymes significantly differ from those of erythrocytes. They are less efficiently inhibited and PFK is activated only by PEP, Fru6P and Pi. The high rate of glycolytic proton formation in Plasmodia inhibits the PFK and thus the anaerobic energy metabolism of the host cell but not that of the parasite. Nevertheless the ATP concentrations in the host and the parasite compartment were found to be nearly identical. This supports the assumption that the parasites make ATP available to their host cell, probably by an adenine nucleotide translocator.

Adenosine Triphosphate↗
PubMed1990

Effect of diamide on polyphosphoinositide metabolism in red blood cells.

In intact red cells diamide had no strong influence on monoester phosphate group turnover of phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP) and phosphatidic acid (PA) due to the potent GSH protection of these pathways in vivo. Following the complete GSH oxidation diamide impaired the turnover of PIP and PA dramatically. However that of PIP2 did not show any change. Indeed, a drastic irreversible decrease of PIP- and PA turnover was caused by a mild oxidative stress with diamide in G6PD deficient red cells.

Azo Compounds↗
PubMed1990

Glucose-6-phosphate dehydrogenase from Plasmodium berghei: kinetic and electrophoretic characterization.

Evidence is given for the existence of a parasite-specific glucose-6-phosphate dehydrogenase in Plasmodium berghei by characterization of its kinetic and electrophoretic properties. After separating the parasites from infected RBC the G6PD was purified by affinity chromatography with 2'5'-ADP-Sepharose 4B. In cellulose acetate electrophoresis malarial G6PD significantly differs from the red cell enzyme. The subunits of the parasite-specific G6PD have a molecular weight of 55 kD in contrast to 59 kD of the RBC enzyme. G6PD from P. berghei shows no cross-reactivity with antibodies against G6PD from rat erythrocytes. The Km-value for G6P of malarial G6PD is increased by one order of magnitude compared with the host cell enzyme.

Animals↗
PubMed1990

Nucleotide status in erythrocytes of rats infected with Pl. berghei.

Nucleotide concentrations in erythrocytes of rats infected with Plasmodium berghei were measured by ion-pair reversed-phase HPLC. UTP and GTP levels were higher in highly infected red blood cells obtained after density separation. The infected red blood cells possess higher hypoxanthine, adenine, and adenosine levels.

Animals↗
PubMed1990

Application of immunological methods for the visualization of PK after IEF in ultrathin layers.

Immunological methods are recommended for protein visualization after IEF on account of their high sensitivity, good specificity and resolution. We used the indirect immunoassay with peroxidase- and 125I-labelled antibodies to investigate microheterogeneity of pyruvate kinase (PK) from human red blood cells and could show a PK pattern with more than 10 single bands. Different methods were tested as to their applicability for protein fixation and subsequent immunological visualization on the polyacrylamide gel. Beside Western blot, immunofixation and ethanolic fixation can be recommended as fixation techniques especially after isoelectric focusing in ultrathin gels.

Collodion↗
PubMed1990

[Classification of glucose-6-phosphate dehydrogenase enzymopathies: evaluation of kinetic parameters using multivariate methods].

The dependence between 9 kinetic parameters of glucose-6-phosphate dehydrogenase from 13 normal controls and 78 G6PD-deficient patients from the GDR and other socialist countries has been investigated by multivariate statistical methods. Using principal component analysis a two-dimensional presentation of the data was obtained from which similarities between individual enzyme variants became detectable. Conclusions could be drawn in how as far the kinetic parameters contribute to the discrimination between different variants. An objective classification of G6PD-variants was achieved by application of cluster analysis. The proposed methods provide an effective means for differential elucidation of G6PD-enzymopathies and should be also useful in the case of other enzymopathies.

Cluster Analysis↗
PubMed1990

Mathematical modelling of energy and redox metabolism of G6PD-deficient erythrocytes.

A mathematical model aimed at the study of erythrocyte metabolism under normal conditions and under glucose 6-phosphate dehydrogenase (G6PD) deficiency has been developed. The degree of deficiency as predicted by the model on the basis of calculated upper limits of oxidative load as well as of maximal methylene blue stimulation correlates with the individual clinical manifestation of the metabolic disease. Therefore, the model permits to judge the degree of metabolic disorder in the presence of G6PD enzymopathies if the kinetic properties of the defect enzyme are known. Experimentally accessible parameters for an assessment of the oxidative load capacity of cells in vivo are proposed. Furthermore, the model predicts that the threshold of tolerance as to energetic load is drastically reduced in the case of severe G6PD deficiency.

Energy Metabolism↗
PubMed1990

Prognosis of hemolytic anemia in G6PD- subjects. Multifactorial cluster analysis of biochemical characteristics of red cell age groups.

Individual susceptibility of 10 G6PD- hemizygotes to oxidative hemolytic agents was tested on the basis of multifactorial cluster analysis of biochemical indices of erythrocyte populations; the indices related to G6PD activity and glucose metabolism were analyzed under physiological and oxidative stress conditions in very young, exactly adult and very old red cell suspensions. Biochemical images of G6PD- erythrocytes were obtained and compared with the donor (7 subjects) biochemical image on a IBM-PC computer according to a special "taxon" program. As a result, a stable subdivision of 10 Gd- biochemical images into 5 taxons was formed; each taxon included G6PD subjects with a certain form of clinical appearance of G6PD deficiency. Multifactorial cluster analysis of biochemical data on the erythrocyte population allows a clinical prognosis for G6PD- subjects.

Anemia, Hemolytic↗
PubMed1990

Heterogeneity of glucose-6-phosphate dehydrogenase enzymopathies in the CSSR.

GdB- variants of 7 patients from the CSSR have been isolated and characterized kinetically. The properties of these G6PD variants differ phenotypically. Among them we found both a variant with a very high Km G6P and a severe chronic hemolytic anemia and one patient with a low Km G6P variant and only intermittent hemolytic crises and moderate hyperbilirubinemia. The low-Km enzyme corresponds to GdMediterranean like variants with a high utilization of substrate analoga and a biphasic pH profile. A third GdB- variant exhibits a low NADP affinity and high inhibition by ATP. A noticeable low utilization of the analogon dNADP was detectable for two enzymes of heterozygotes.

Czechoslovakia↗
PubMed1990

Classification of glucose-6-phosphate dehydrogenase variants by multivariate statistical analysis.

Using principal component analysis a two-dimensional presentation of kinetic parameters from various G6PD-variants was obtained from which similarities between individual enzymes became detectable. Conclusions could be drawn as to how far the kinetic parameters contribute to the discrimination between different variants. An objective classification of G6PD-variants was achieved by application of cluster analysis. The proposed methods provide an effective means for differential elucidation of G6PD-variants and other heterogeneous enzymopathies.

Cluster Analysis↗
PubMed1990

IEF-microheterogeneity of human PK-R: applicability for prenatal diagnosis.

Microheterogeneity of human erythrocyte pyruvate kinase (PK-R) can be obtained by isoelectric focusing (IEF) in ultrathin polyacrylamide gels followed by immunological visualization methods. Using this method to study whether a polymorphismus of PK-R occurs, we could not find any deviations from the normal PK pattern in the case of samples from 100 German donors as well as at a lower number of PK samples from European, African and Asian donors. Furthermore, we compared the IEF-pattern of PK mutants with that of normal new-borns and of foetal PK-samples. Our results show that IEF-microheterogeneity of PK may serve as a tool for prenatal diagnosis in the case of families which are effected by a severe PK deficiency.

Erythrocytes↗