Mature Human Erythrocytes Research Articles

Uridine-diphosphoglucose glucosyltransferase in human erythrocytes

The presence of glucosyltransferase activity in mature human erythrocytes and leukocytes has been established both by demonstration of UDP formation from UDPG, and by incorporation of [ 14C] glucose from UDP-[ 14C] glucose into glycogen. The erythrocyte and leukocyte enzymes have similar properties and both require glucose 6-P for activity. The enzyme activity per white cell is about 400 times that per red cell. The erythrocyte glucosyltransferase activities did not differ from that in the normal in two patients with hepatic glucosyltransferase deficiency and in other patients with a variety of carbohydrate abnormalities.

Cytoplasmic characteristics of human erythrocyte malic dehydrogenase

Malic dehydrogenase in the mature human erythrocyte possesses the properties of the cytoplasmic form of the enzyme. The red cell contains a large quantity of malic dehydrogenase in contrast to the absence or minimal activity of certain other enzymes in this tissue which also exist in the cytoplasmic and mitochondrial form. A possible role for malic dehydrogenase in the metabolism of the erythrocyte has been suggested.

Glycolysis in young and mature normal human erythrocytes.

CONSIDERABLE data exist concerning the decline of metabolic activity which occurs during the normal ageing of human erythrocytes. In particular, several of the glycolytic enzymes are present in higher concentration in younger cells (that is, reticulocytes). This is true of phosphohexoisomerase1,2, triosephosphate dehydrogenase3, aldolase2, glucose-6-phosphate dehydrogenase and 6-phosphogluconic dehydrogenase1,4. However, in the assay methods used the maximum activity of these enzymes is measured at their optimum pH in dilute haemolysates containing added excess of substrate, coenzyme and activator; these are conditions which do not obtain in intact erythrocytes. Indeed, the results of Chapman et al.5 demonstrate that glucose consumption in normal intact erythrocytes proceeds at a rate less than that calculable from the concentrations of Embden–Meyerhof pathway enzymes that are present. It does not follow, therefore, that the presence of higher concentrations of glycolytic enzymes, as in reticulocytes, produces an increased rate of glycolysis. However, Bernstein2 showed that glucose consumption and lactate production in intact erythrocytes were, in fact, increased in proportion to the reticulocyte concentration of the samples.

Purification and properties of human-erythrocyte malic dehydrogenase.

1. 1. A 3000-fold purification of malic dehydrogenase was obtained from the mature human erythrocyte. 2. 2. The effect of pH on activity was studied and the apparent Michaelis constants for the substrates and cofactors determined. The properties reported herein for the enzyme from the mature human erythrocyte corresponded closely to those reported by other investigators for malic dehydrogenase from other sources. 3. 3. The possibility is presented that the malic dehydrogenase isolated from the mature human erythrocyte may be the cytoplasmic form of the enzyme.

Purification and properties of human-erythrocyte malic dehydrogenase

Abstract 1. 1. A 3000-fold purification of malic dehydrogenase was obtained from the mature human erythrocyte. 2. 2. The effect of pH on activity was studied and the apparent Michaelis constants for the substrates and cofactors determined. The properties reported herein for the enzyme from the mature human erythrocyte corresponded closely to those reported by other investigators for malic dehydrogenase from other sources. 3. 3. The possibility is presented that the malic dehydrogenase isolated from the mature human erythrocyte may be the cytoplasmic form of the enzyme.

Magnesium Metabolism of Human and Rabbit Erythrocytes

Abstract A modification of the magnesium ammonium phosphate precipitation method for the determination of serum magnesium was devised to determine the magnesium content of erythrocytes. The concentration of magnesium in the red cells of healthy hospital personnel was 4.67 ± 0.92 mEq./L. An increase in erythrocyte magnesium concentration was observed in patients with reticulocytosis. Experimental production of reticulocytosis by the administration of phenylhydrazine to rabbits confirmed these clinical observations. No significant in vitro uptake of Mg28 from the suspending medium occurred in mature human erythrocytes or in mature or immature erythrocytes from rabbits. The relative tissue uptake of Mg28 in the bone marrow was significantly increased in animals in whom anemia and marked reticulocytosis were produced by phenylhydrazine. Relative activity was decreased in the hearts, spleens, and kidneys of these animals. Since there is no evidence for significant exchange of magnesium in immature or mature erythrocytes in the peripheral circulation, it is concluded that the magnesium content of erythrocytes is increased in the bone marrow prior to their release into the peripheral circulation.

A new haemoprotein with a unique iron porphyrin prosthetic group isolated from human erythrocytes.

HAEMOGLOBIN, comprising more than 95 per cent of the protein of the red cell, is the major protein in the mature human erythrocyte. The extremely high concentration of this compound in the red cell renders very difficult the identification of other haemoproteins in the erythrocyte. Catalase is one haemoprotein which has been isolated from erythrocytes. A third haemoprotein, spectrally similar to haemoglobin but which has been reported to be functional in the methaemoglobin reductase system, has also been reported1,2. It is the purpose of this communication to present observations on still another haemoprotein which has been isolated from normal human erythrocytes. This compound is particularly noteworthy since its prosthetic group appvears to be different from any previously reported naturally occurring iron porphyrin.