2,3-Bisphosphoglycerate

From Wikipedia, the free encyclopedia

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (November 2007)

2,3-Bisphosphoglycerate
IUPAC name	2,3-Bisphosphoglycerate
Other names	2,3-diphosphoglycerate
Identifiers
Abbreviations	2,3-BPG, 2,3-DPG, 23BPG
CAS number	[138-81-8]
PubChem	61
Properties
Molecular formula	C3H8O10P2
Molar mass	266.037
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

2,3-Bisphosphoglycerate (2,3-BPG, also known as 2,3-diphosphoglycerate or 2,3-DPG) is a three carbon isomer of the glycolytic intermediate 1,3-bisphosphoglycerate. 2,3-BPG is present in human red blood cells (RBC; erythrocyte) at approximately 5 mmol/L. It binds with greater affinity to deoxygenated hemoglobin (e.g. when the red cell is near respiring tissue) than it does to oxygenated hemoglobin (e.g. in the lungs). In bonding to partially deoxygenated hemoglobin it allosterically upregulates the release of the remaining oxygen molecules bound to the hemoglobin, thus enhancing the ability of RBCs to release oxygen near tissues that need it most.

Recently, scientists have found the similarities between low amounts of 2,3-BPG with the occurrence of HAPE at high altitudes.

Its function was discovered in 1967 by Reinhold Benesch and Ruth Benesch.^[1]

Contents 1 Metabolism 2 Effects of binding 3 Fetal hemoglobin 4 References 5 External links

[edit] Metabolism

2,3-BPG is formed from 1,3-BPG by an enzyme called bisphosphoglycerate mutase. It is broken down by a phosphatase to form 3-phosphoglycerate. Its synthesis and breakdown are therefore a way around a step of glycolysis.

                       glycolysis
              1,3-BPG ------------> 3-PG
                   \_               _^
                     \_           _/
              2,3-BGP  v         /  2,3-BPG
               mutase     2,3-BPG   phosphatase

[edit] Effects of binding

When 2,3-BPG binds deoxyhemoglobin, it acts to stabilize the low oxygen affinity state (T state) of the oxygen carrier. It fits neatly into the cavity of the deoxy- conformation, exploiting the molecular symmetry and positive polarity by forming salt bridges with lysine and histidine residues in the four subunits of hemoglobin. The R state, with oxygen bound to a heme group, has a different conformation and does not allow this interaction.

By selectively binding to deoxyhemoglobin, 2,3-BPG stabilizes the T state conformation, making it harder for oxygen to bind hemoglobin and more likely to be released to adjacent tissues. 2,3-BPG is part of a feedback loop that can help prevent tissue hypoxia in conditions where it is most likely to occur. Conditions of low tissue oxygen concentration such as high altitude (2,3-BPG levels are higher in those acclimated to high altitudes), airway obstruction, or congestive heart failure will tend to cause RBCs to generate more 2,3-BPG in their effort to generate energy by allowing more oxygen to be released in tissues deprived of oxygen. Ultimately, this mechanism increases oxygen release from RBCs under circumstances where it is needed most. This release is potentiated by the Bohr effect in tissues with high energetic demands.

[edit] Fetal hemoglobin

Interestingly, fetal hemoglobin (HbF) exhibits a low affinity for 2,3-BPG, resulting in a higher binding affinity for oxygen. This increased oxygen binding affinity relative to that of adult hemoglobin (HbA) is due to HbF having two α/γ dimers as opposed to the two α/β dimers of HbA. The positive histidine residues of HbA β-subunits that are essential for forming the 2,3-BPG binding pocket are replaced by serine residues in HbF γ-subunits.

[edit] References

This article or section includes a list of references or external links, but its sources remain unclear because it lacks in-text citations. You can improve this article by introducing more precise citations.

1. ^ Benesch, R.; Benesch, R.E. (1967). "The effect of organic phosphates from the human erythrocyte on the allosteric properties of hemoglobin.". Biochem Biophys Res Commun 26 (2): 162–7. doi:10.1016/0006-291X(67)90228-8. 

• Berg, J.M., Tymockzko, J.L. and Stryer L. Biochemistry (5th ed). W.H. Freeman and Co, New York, 1995. ISBN 0-7167-4684-0.
• -684392408 at GPnotebook
• Online medical dictionary

[edit] External links

• A live model of the effect of changing 2,3 BPG on the oxyhaemoglobin saturation curve

v • d • e Respiratory system, physiology: respiratory physiology Volumes lung volumes - vital capacity - functional residual capacity - respiratory minute volume - closing capacity - dead space - spirometry - body plethysmography - peak flow meter - thoracic independent volume - bronchial challenge test Airways ventilation (V) (positive pressure) - breath (inhalation, exhalation) -respiratory rate - respirometer - pulmonary surfactant - compliance - hysteresivity - airway resistance Blood pulmonary circulation - perfusion (Q) - hypoxic pulmonary vasoconstriction - pulmonary shunt Interactions ventilation/perfusion ratio (V/Q) and scan - zones of the lung - gas exchange - pulmonary gas pressures - alveolar gas equation - hemoglobin - oxygen-haemoglobin dissociation curve (2,3-DPG, Bohr effect, Haldane effect) - carbonic anhydrase (chloride shift) - oxyhemoglobin - respiratory quotient - arterial blood gas - diffusion capacity - Dlco Control of respiration pons (pneumotaxic center, apneustic center) - medulla (dorsal respiratory group, ventral respiratory group) - chemoreceptors (central, peripheral) - pulmonary stretch receptors (Hering-Breuer reflex) Insufficiency high altitude - oxygen toxicity - hypoxia