A 28-year-old Indian male presents to the emergency department with severe hemolytic anemia following consumption of fava beans. Laboratory investigations reveal hemoglobin 7.2 g/dL, reticulocyte count 8.5%, and elevated indirect bilirubin. Peripheral blood smear shows Heinz bodies. Urine dipstick is positive for blood but RBCs are absent. Which of the following enzyme deficiencies is most likely responsible for this clinical presentation?