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Biomedical subjects

D Maretzki

Publications and source records attributed to D Maretzki.

7 recordsLinked to original sources
PubMed1979

[Selectivity of action of the lipoxygenase from rabbit reticulocytes on mitochondria and erythrocyte membranes].

Whereas the lipoxygenase from rabbit reticulocytes caused a large formation of malonyl dialdehyde (MDA) with rat liver mitochondria, erythrocyte ghosts were attacked only slightly independently of their type of preparation. The formation of MDA was not enhanced by release of spectrin-actin from the ghosts. The lipoxygenase did not give rise to hemolysis of intact erythrocytes. The formation of MDA was increased by heat treatment of the ghosts. Addition of cholesterol to a phospholipid emulsion inhibited the formation of MDA by the reticulocyte lipoxygenase. These results indicate that both lipid-protein interactions and the cholesterol content of the membranes may be involved in the preferential attack of the lipoxygenase on mitochondrial membranes.

Animals↗
PubMed1979

The breakdown of adenine nucleotides in glucose-depleted human red cells.

1) The rate of 2,3-bisphosphoglycerate breakdown is independent of pH value. 2) The adenine nucleotide pattern at alkaline pH values with its characteristic lowering of ATP and the accompanying accumulation of fructose-1,6-bisphosphate is caused by a relative excess of the activity of the hexokinase-phosphofructokinase system as compared wity pyruvate kinase. 3) The breakdown of adenine nucleotides proceeds via AMP mainly through phosphatase and not via AMP deaminase. 4) The constancy of the sum of nucleotides as long as glucose is present is postulated to be due to resynthesis via adenosine kinase which competes successfully with adenosine deaminase. 5) A procedure is given to calculate ATPase activity of glucose-depleted red cells. The results indicate that the ATPase activity is less at lower pH values and declines with time. An ATPase with a high Km for ATP is postulated. 6) During glucose depletion ATP production is mostly derived from the breakdown of 2,3-bisphosphoglycerate and the supply from the pentose phosphate pool both of which proceed at a constant rate. The contribution of pentose phosphate from the breakdown of adenine nucleotides amounts to 40% of the lactate formed at pH 6.8 and is about twice the lactate at pH 8.1.

Adenine Nucleotides↗
PubMed1978

Immunochemical studies on human glyceraldehyde-3-phosphate dehydrogenase.

Highly purified GAPD preparations from human erythrocytes and skeletal muscle have been used as immunogenes in rabbits. The antibodies produced readily precipitated their antigens and also inhibited their enzymatic activities. An immunochemical evaluation of the precipitability of both enzymes exhibited no immunochemical differences between them. Furthermore, the antibodies were tested against several tissue homogenates from man and revealed an identical precipitability. The identical cross-reactivity indicating a lack of antigenic differences support the absence of GAPD-isoenyzmes in man. The amount of GAPD in several organ extracts was estimated by the technique of single radial immunodiffusion. Furthermore it was demonstrated that the GAPD is bound to the membrane only under hypotonic conditions of hemolysis, while under approximated intracellular conditions of hemolysis the GAPD is not membrane bound.

Animals↗
PubMed1975

[Control intensity of glycolytic enzymes in ultrasonic hemolysates of erythrocytes].

By addition of enzyme the control intensity was determined on the pacemaker enzymes hexokinase and phosphofructokinase, as well as on glyceraldehyde-3-phosphate-dehydrogenase and the pyruvate kinase with a control intensity of almost 0 in ultrasonic hemolysates from erythrocyte concentrate. This hemolysate approximately reflects the conditions existing in the intact cell with regard to glycolytic rate, ATP supply, and metabolite concentration. It is therefore suitable as a cell model, excluding the membrane, for studying inner control factors. For HK, PFK, GAPD, and PK predictions based on the linear glycolytic model about the significance of these enzymes for the regulation of the glycolytic rate could be confirmed.

Erythrocytes↗