Intracellular free magnesium and phosphorylated metabolites in hexokinase- and pyruvate kinase-deficient red cells measured using 31P-NMR spectroscopy.
The erythrocyte metabolism of two patients with nonspherocytic hemolytic anemia caused by a hexokinase deficiency, and a pyruvate kinase deficiency, respectively, were studied with NMR. The complexing of ATP and 2,3-diphosphoglycerate (2,3-DPG) with Mg2+ and hemoglobin (Hb) was determined using 31P-NMR on oxygenated and deoxygenated cells to investigate the influences of these enzyme defects on intracellular magnesium distribution and on Hb oxygen dissociation. In the pyruvate kinase-deficient red blood cells, the 2,3-DPG concentration was almost twice the normal value and the ATP concentration was near the lower limit of the normal range. In the hexokinase-deficient red cell population, the predominance of young cells masked the deficiency. Therefore, reticulocyte control cells were included in this study. In the oxygenated pyruvate kinase-deficient cells, the fraction of ATP that is complexed to magnesium as well as the free Mg2+ concentration were normal, despite the abnormal concentration of 2,3-DPG. In the deoxygenated cells the free Mg2+ concentration was lower than in normal cells. The fraction of Hb complexed with 2,3-DPG was higher than normal in both oxygenated and deoxygenated pyruvate kinase-deficient cells, in accordance with the high p50 of the oxygen-hemoglobin dissociation curve. In hexokinase-deficient cells, two major abnormalities are found: when the cells were deoxygenated, the concentration of ATP and 2,3-DPG fell. This was not observed for any other sample and could, therefore, be a consequence of the hexokinase deficiency. Despite almost normal levels of magnesium-binding metabolites, the free Mg2+ concentration in oxygenated and deoxygenated cels is much lower than in normal cells. This could be a cell-age-related phenomenon, since lower free Mg2+ concentrations were also found in reticulocyte control cells.
Ouwerkerk
R
R
Department of Haematology, University Hospital, Utrecht, The Netherlands.
van Echteld
C J
CJ
Staal
G E
GE
Rijksen
G
G
D019794:2,3-Diphosphoglycerate; D000255:Adenosine Triphosphate / Q000097:blood*; D004163:Diphosphoglyceric Acids / Q000097:blood*; D004912:Erythrocytes / Q000032:analysis*; D006454:Hemoglobins / Q000032:analysis; D006593:Hexokinase / Q000172:deficiency*; D006801:Humans; D008274:Magnesium / Q000097:blood*; D009682:Magnetic Resonance Spectroscopy; D010100:Oxygen / Q000378:metabolism; D011770:Pyruvate Kinase / Q000172:deficiency*
D004163:Diphosphoglyceric Acids; D006454:Hemoglobins; D019794:2,3-Diphosphoglycerate; D000255:Adenosine Triphosphate; D006593:Hexokinase; D011770:Pyruvate Kinase; D008274:Magnesium; D010100:Oxygen