A patient presents with anemia characterized by a marked reduction in haptoglobin levels and an increase in bilirubin, suggestive of intravascular hemolysis. Which enzyme deficiency is most likely responsible for this condition?

G6PD deficiency leads to a reduction in the enzyme that protects red blood cells from oxidative stress, making them more susceptible to hemolysis under certain conditions, which can result in intravascular hemolysis characterized by low haptoglobin and high bilirubin levels.