Question

Mature erythrocytes lack a nucleus, mitochondria, and other organelles. A relatively common inherited disease involves a mutation in pyruvate kinase (PK) (an autosomal recessive trait most commonly found in those of Northern European ancestry). Symptoms of compromised PK activity include low concentrations of ATP and high concentrations of 2,3BPG (2,3-bisphosphoglycerate). Under these conditions, red bloods cells have short half lives and result in hemolytic anemia.

a. What accounts for the low ATP levels?        

b. Why would there be high levels of 2,3BPG?

c. What effect will 2,3BPG have on the oxygen carrying ability of the red blood cells?

Answer 1

a. Mutation in pyruvate kinase dose not allow the last step of glycolysis (see figure). So net gain of atp is 0 in anaerobic condition.

b. Accumulation of intermediate product 2,3- bpg as mutated pk can't convert phosphoenol pyruvate to pyruvate and backward proceses are reversible.

c. Incresed level of 2,3-bpg in RBC decreses the oxygen binding ability of haemoglobin. So fast unloading of oxygen molecules occur. Abnormal red blood cells gatherd by the spleen and destoyed resulting haemolytic anaemia.