2,3-Diphosphoglycerate phosphatase/synthase: a potential target for elevating the diphosphoglycerate level in human red blood cells.
To exploit the well documented effect of 2,3-diphosphoglyceric acid (2,3-DPG) in enhancing oxygen delivery by human erythrocytes, we have investigated whether the DPG synthase/phosphatase enzyme system can be targeted to increase DPG levels in the cell. The hydrolytic activity (phosphatase) of the DPG metabolizing enzyme complex exhibits a marked dependence on a physiological effector, 2-phosphoglycolate. Little phosphatase activity is detected in the absence of this activator irrespective of the concentrations of the substrate. The phosphoglycolate-dependent phosphatase activity is competitively inhibited by a glycolytic intermediate, 3-phosphoglyceric acid (3-PGA). The 3-PGA inhibition persists when the 2,3-DPG concentration is raised to saturation level. In contrast, 3-PGA enhances the DPG synthase activity in a dose-dependent manner. In intact red cells, one-half of the cellular DPG content is depleted after 6 hr at 37 degrees C in glucose-free medium. The rate of 2,3-DPG degradation is accelerated when the cellular level of phosphoglycolate is increased by incubation with exogenous glycolate. Together, these results indicate that 2,3-DPG content in erythrocytes can be directly regulated through modulation of phosphatase/synthase activities. In support of this notion, a pyruvate kinase inhibitor, L-alanine, increases by 2-fold the cellular 3-PGA level. This is accompanied by a significant increase (30%) in 2,3-DPG content in human red blood cells. It is postulated that the DPG-promoting action of 3-PGA is mediated through simultaneous phosphatase inhibition and synthase activation. Furthermore, as a result of increased DPG accumulation, the oxygen-hemoglobin dissociation curve in L-alanine-treated cells is rightward shifted by 2.5 torr.
Yu
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KT
Rorer Central Research, King of Prussia, Pennsylvania.
Pendley
C
C
Herczeg
T
T
Pendleton
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RG
D019794:2,3-Diphosphoglycerate; D000409:Alanine / Q000494:pharmacology; D004163:Diphosphoglyceric Acids / Q000097:blood*; D004912:Erythrocytes / Q000378:metabolism*; D005988:Glyceric Acids / Q000097:blood; D006016:Glycolates / Q000494:pharmacology; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D010108:Oxyhemoglobins / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000502:physiology*
D004163:Diphosphoglyceric Acids; D005988:Glyceric Acids; D006016:Glycolates; D010108:Oxyhemoglobins; C019794:bisphosphoglycerate phosphatase; D019794:2,3-Diphosphoglycerate; C005156:3-phosphoglycerate; D010744:Phosphoric Monoester Hydrolases; C013193:phosphoglycolate; D000409:Alanine