Which enzyme deficiency causes hemolytic anaemia –
Glucose 6 phosphate dehydrogenase (G6PD) deficiency

Normally, RBCs are protected from oxidant injury by reduced glutathione.
Reduced glutathione is generated from oxidized glutathione and the reducing equivalent for this reaction is provided by NADPH.
This NADPH is generated in HMP shunt by enzyme Glucose-6-phosphate dehydrogenase, while oxidizing glucose-6-phosphate.
If G6PD is deficient, NADPH production will be reduced that results in increased susceptibility of RBC to oxidative damage because of unavailability of reduced glutathione.
So, whenever there is oxidant stress, e.g. by drugs, infection or foods, hemolysis occurs.
G6PD deficiency causes episodic intravascular and extravascular hemolysis. Important peripheral smear findings → Heinz bodies, Bite cells, Spherocytes.
G–6–PD
Aldolase
Isomerase
Enolase