Roles of hemoglobin Allostery in hypoxia-induced metabolic alterations in erythrocytes: simulation and its verification by metabolome analysis.
When erythrocytes are exposed to hypoxia, hemoglobin (Hb) stabilizes in the T-state by capturing 2,3-bisphosphoglycerate. This process could reduce the intracellular pool of glycolytic substrates, jeopardizing cellular energetics. Recent observations suggest that hypoxia-induced activation of glycolytic enzymes is correlated with their release from Band III (BIII) on the cell membrane. Based on these data, we developed a mathematical model of erythrocyte metabolism and compared hypoxia-induced differences in predicted activities of the enzymes, their products, and cellular energetics between models with and without the interaction of Hb with BIII. The models predicted that the allostery-dependent Hb interaction with BIII accelerates consumption of upstream glycolytic substrates such as glucose 6-phosphate and increases downstream products such as phosphoenolpyruvate. This prediction was consistent with metabolomic data from capillary electrophoresis mass spectrometry. The hypoxia-induced alterations in the metabolites resulted from acceleration of glycolysis, as judged by increased conversion of [(13)C]glucose to [(13)C]lactate. The allostery-dependent interaction of Hb with BIII appeared to contribute not only to maintenance of energy charge but also to further synthesis of 2,3-bisphosphoglycerate, which could help sustain stabilization of T-state Hb during hypoxia. Furthermore, such an activation of glycolysis was not observed when Hb was stabilized in R-state by treating the cells with CO. These results suggest that Hb allostery in erythrocytes serves as an O(2)-sensing trigger that drives glycolytic acceleration to stabilize intracellular energetics and promote the ability to release O(2) from the cells.
Kinoshita
Ayako
A
Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan.
Tsukada
Kosuke
K
Soga
Tomoyoshi
T
Hishiki
Takako
T
Ueno
Yuki
Y
Nakayama
Yoichi
Y
Tomita
Masaru
M
Suematsu
Makoto
M
D002248:Carbon Monoxide / Q000378:metabolism; D015687:Cell Hypoxia; D004912:Erythrocytes / Q000201:enzymology*; D006019:Glycolysis; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism; D020543:Proteome / Q000378:metabolism*
D006454:Hemoglobins; D020543:Proteome; D002248:Carbon Monoxide; D010100:Oxygen