Question

The constant interconversion of 3-phospho-D-glycerate (3PG), 3-phospho-D-glyceroyl phosphate (1,3DPG) and 2,3-disphospho-D-glycerate at the expense of ATP, in red blood cells, serve as a fine control mechanism for both ATP levels and the oxygenation/deoxygenation status of haemoglobin.

What type of regulation is this ?

Answer 1

This cycle is rapaport lumbering cycle.

Here 1, 3 bis phospoglycerate intermediate of glycolysis converted in to 2, 3 bis phospoglycerate and finally in 3 phospoglycerate with out production of ATP. In glycolysis, during conversion of 1, 3 bisphosphoglycerate in to 3 phospoglycerate there is production of ATP occurs. So whenever energy is sufficient this altered pathway is used which complete the cycle with less production of ATP.

Secondary this 2, 3BPG also act as allosteric modulator which regulates oxygenation and deoxygenation of RBC. This 2,3BPG binds to oxyHb and lead to release more and more oxygen at the tissue level. Thus this 2,3 BPG shift oxygen dissociation curve to right side and release more and more oxygen from oxyHb and a t as a negative allosteric modulator.