Glucose 6 Phosphate Dehydrogenase an overview ScienceDirect Topics Although G6PD deficiency, which can cause problems in red blood cells upon certain triggers, is the most common human enzyme defect, affecting over 400 million people, including over 1 in 10 Black In G6PD deficiency (XR), we have increased oxidative damage to RBCs, leading to intravascular hemolysis with decreased serum haptoglobin. We have decreased NADPH production, which means decreased conversion of oxidized ( S S ) glutathione Glucose 6 phosphate Dehydrogenase (G6PD) Enzyme ROS Scavenger Biochemistry & Hematology