Pyridine nucleotides in erythrocyte metabolism.

Abstract

In recent years investigations of erythrocyte metabolism have been concerned with the interrelationships of enzymes, coenzymes, substrates, cofactors, and pH, inter alia (1-8). Although data have accumulated on these various aspects of the metabolism of normal and pathological erythrocytes, little direct information has been available heretofore on pyridine nucleotide coenzymes, despite their importance in both the glycolytic and the hexose monophosphate shunt pathways. The availability of these compounds in the blood of immature subjects is of particular interest because of certain abnormalities in the erythrocytes of fullterm newborn and prematurely born infants. These abnormalities, which include decreased survival of 51Cr-labeled erythrocytes in premature infants (9, 10) and increased susceptibility to Heinz body formation (11) and to methemoglobinemia (12-15) in both full-term and premature infants, as well as the occurrence of unexplained hemolytic anemias, suggest the possibility of transient biochemical defects in the erythrocytes of these young subjects. Although the activities of the pyridine nucleotide-dependent enzymes in both the glycolytic and shunt pathways are increased in the erythrocytes of young infants (16,17), the levels of the oxidized and reduced coenzymes themselves have not been reported.In the present study the concentrations of DPN,l

Current knowledge concerning optimum nutritional status of riboflavin, niacin and pyridoxine

“…NADP on the other hand showed no significant response to differences in niacin intake over the range of 6·1-32 niacin equivalents. This relative insensitivity of erythrocyte NADP to niacin intake has also been reported in other studies in human subjects (Gross et al 1960). NAD : NADP in erythrocytes or whole blood may be a useful variable when there are disturbances to haemoglobin synthesis or erythrocyte production.…”

“…This enzyme catalyses the conversion of nicotinic acid to nicotinic mononucleotide. Although enzyme activity has been shown to increase in response to niacin depletion in pigs (Arienti et al 1982), such an effect was not seen in rats (Shibata & Matsuo, 1989), and activity was not found to be responsive to changes in niacin intakes in human subjects over a short period (Gross et al 1960).…”

Genetic Variants of Human Erythrocyte Glucose‐6‐Phosphate Dehydrogenase

“…the medium and high stability states, have been demonstrated, depending on the level of NADP+. The transition from medium to high stability takes place a t a concentration of NADP+ much higher than found in the red cell [18,19], and higher than the association constants previously determined [S, 171 ; however, this is true for measurements carried out at the very unphysiological temperature of 49-56 "C. It is quite possible that the NADP+ concentrations required to cause the transition a t 37 "C may be 10-fold lower1. Thus, the ',high stability" form of the enzyme may be physiologically important.…”

Regulierende Faktoren der Methylenblaukatalyse in Erythrocyten

“…Berechnet man aus den Literaturdaten fur cellulare NADP+-Konzentrationen die Vmax der intakten Zellen, werden Werte von 18,[8][9][10][11][12][13][14][15][16][17][18][19][20]4mMol/lZellen x h erhalten. Sie sind ca.…”