Control of oxygen affinity of hemoglobin in K562 cells induced by hemin.
The oxygen affinity of hemoglobin in K562 cells induced by hemin and the relationship between levels of 2,3-diphosphoglycerate (2,3-DPG) and hemoglobin have been investigated. Absorption spectra of induced cells indicate that the hemoglobin is oxygenated; oxygen dissociation curves are symmetric, with a P50 of 20 +/- 0.9 mm Hg, Hill coefficient of 2.5, and a normal temperature dependence. The intracellular pH measured by phosphorus 31 nuclear magnetic resonance (NMR) was 7.3. The amount of 2,3-DPG was determined by an enzymatic method and by 31P NMR. The level of 2,3-DPG in uninduced K562 cells, containing 0.5 pg of hemoglobin per cell, was low (5 +/- 0.5 mumole/10(8) cells), but increased to 64 +/- 5 mumole/10(8) cells upon induction of hemoglobin accumulation (to a final level of 20 pg hemoglobin/cell). For several experiments, there was a closely coordinated relationship between 2,3-DPG and hemoglobin levels, at about 1:1 stoichiometry of the two molecules. The time course of induction of hemoglobin, and of 2,3-DPG levels, are very similar; both processes are reversible. These data suggest that induction of hemoglobin synthesis in K562 cells by hemin results in hemoglobin-containing cells with normal oxygenation properties and that 2,3-DPG and hemoglobin levels are coordinately controlled in these cells. Elucidation of the mechanism of this effect should be of importance in understanding the erythroid-like differentiation of these cells.
D000255:Adenosine Triphosphate / Q000097:blood; D002460:Cell Line; D042966:Cytochrome-B(5) Reductase / Q000378:metabolism; D004163:Diphosphoglyceric Acids / Q000097:blood; D005319:Fetal Hemoglobin / Q000096:biosynthesis; D006418:Heme / Q000031:analogs & derivatives*; D006427:Hemin / Q000494:pharmacology*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007951:Leukemia, Myeloid / Q000378:metabolism*; D008274:Magnesium / Q000097:blood; D009682:Magnetic Resonance Spectroscopy; D010101:Oxygen Consumption; D010758:Phosphorus / Q000097:blood
D004163:Diphosphoglyceric Acids; D006454:Hemoglobins; D010758:Phosphorus; D006418:Heme; D006427:Hemin; D000255:Adenosine Triphosphate; D005319:Fetal Hemoglobin; D042966:Cytochrome-B(5) Reductase; D008274:Magnesium