title: The diurnal rhythm of enzymes in human red cells.
abstract: The activities of glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP oxidoreductase, G6PD), 6-phosphogluconate dehydrogenase (6-phospho-d-gluconate: NADP oxidoreductase, 6PGD), hexokinase (ATP:D-hexose 6-phosphotransferase, HK), lactic dehydrogeanse (L-lactate: NAD oxidoreductase, LDH) and aspirate aminotransferase (L-aspartate: 2-oxoglutarate aminotransferase, Asp.T) were determined in red blood cells of 11 healthy individuals. The determinations were carried out on samples drawn every 4 h over a 24 h period. The activities of G6PD, 6PGD, LDH and Asp.T exhibited a semi-circadian rhythm, namely, two peaks of activity during 24 h while HK activity demonstrated a true circadian rhythm. In addition a polymorphism of the G6PD and LDH activity patterns was observed. The implications of a biological clock in enucleated cells are discussed.
mesh_terms: D001219:Aspartate Aminotransferases / Q000097:blood; D002940:Circadian Rhythm; D004912:Erythrocytes / Q000201:enzymology*; D005954:Glucosephosphate Dehydrogenase / Q000097:blood; D006593:Hexokinase / Q000097:blood; D006801:Humans; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000097:blood; D010734:Phosphogluconate Dehydrogenase / Q000097:blood
chemical_list: D007770:L-Lactate Dehydrogenase; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D001219:Aspartate Aminotransferases; D006593:Hexokinase