<prompt> Answer this question truthfullyWhat is the relationship between pyruvate kinase deficiency and the levels of 2,3-BPG, and how does this affect the oxygen-carrying capacity of hemoglobin?  <response>: <reason> Pyruvate kinase deficiency is a rare genetic disorder that can lead to increased levels of 2,3-BPG in red blood cells. This molecule is a byproduct of glycolysis, and normally helps to regulate the affinity of hemoglobin for oxygen. However, in excess amounts, 2,3-BPG can cause hemoglobin to release oxygen more readily, which can lead to decreased oxygen-carrying capacity of the blood. This can result in symptoms such as fatigue, shortness of breath, and anemia. 