Pentose phosphate pathway with a breakdown in the conversion of<unk><unk><unk>  to ribulose-5-phosphate due to a deficiency of<unk><unk><unk>  enzyme Reaction mechanism<unk><unk><unk>  <unk> PGD) is an enzyme in the pentose phosphate pathway (see image).<unk> PGD catalyzes the reaction of<unk><unk>  to an unstable form of 3-keto-6-phosphogluconate, and yields a co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH) as a byproduct. NADPH supplies reducing power to cells. The reaction is the second NADPH releasing reaction in the pentose phosphate pathway, the first being catalyzed by glucose-6-phosphate<unk> . 3-keto-6-phosphogluconate then rapidly (in an irreversible reaction) decarboxylates to CO2 and ribulose-5-phosphate, which is the precursor to many vital metabolic processes. Importance of NADPH The NADPH pathway (both<unk> PGD and G6PD reactions) is the only source of reductant to reduce glutathione in red blood cells. The role of erythrocytes as oxygen carriers puts them at risk of being damaged by oxidizing free radicals. The reduction of glutathione acts as an antioxidant and prevents damage from reactive oxygen species. Oxidative stress People suffering from<unk> PGD or G6PD deficiency (or both) are at risk of hemolytic anemia in states of oxidative stress. Oxidative stress can result from infection and from chemical exposure to medication and certain foods. Broad beans, e.g., fava beans, contain high levels of vicine, divicine, convicine and isouramil, all of which are oxidants. When all remaining reduced glutathione is consumed, enzymes and other proteins, such as hemoglobin are subsequently damaged by the free radicals, leading to electrolyte imbalance, cross-bonding and protein deposition in the red cell membranes. Damaged red cells are phagocytosed and sequestered (taken out of circulation) in the spleen. The hemoglobin is metabolized to bilirubin (causing jaundice). The red blood cells rarely disintegrate in the circulation, so hemoglobin is rarely excreted directly by the kidney, but this can occur in severe cases, causing acute kidney injury.
6-phosphogluconate dehydrogenase deficiency
Glutaminase deficiency
Ribose-5-phosphate isomerase deficiency
Pyruvate kinase deficiency
Malonyl-CoA decarboxylase deficiency
Pyruvate carboxylase deficiency
3-Methylcrotonyl-CoA carboxylase deficiency
D-glycerate dehydrogenase deficiency