PENTOSE PHOSPHATE PATHWAY.pptx

biochemistry

1. PENTOSE PHOSPHATE PATHWAY Prepared by, Bincy Cherian Assistant professor cnk

2. INTRODUCTION It is also called hexose monophosphate shunt (HMP shunt). It is the second major pathway for metabolism of glucose.

3. Sites This pathway occurs in liver, erythrocytes, lactating mammary glands, testes and adipose tissue. Enzymes of this pathway is found in cytosol.

4. STEPS

5. reaction Oxidative Phase B. Non-Oxidative Phase

6. Significance of the Pathway The oxidative phase of the pathway is seen in the above organs, where NADPH generation is required for lipid synthesis or steroid synthesis. The non-oxidative phase is present in all tissues, and so synthesis of ribose is possible in all tissues of the body. The major metabolic role of the pathway is to provide cytoplasmic NADPH for reductive biosynthesis of fatty acids, cholesterol and steroids. Free radicals (super oxide, hydrogen peroxide) are continuously produced in all cells. Erythrocyte Membrane Integrity NADPH is required by the RBC Prevention of Met- hemoglobinemia NADPH is also required to keep the iron of hemoglobin in the reduced (ferrous) state and to prevent the accumulation of met- hemoglobin . Met- hemoglobin cannot carry oxygen. Detoxification of Drugs Most of the drugs and other foreign substances are detoxified by the liver microsomal enzymes, with the help of NADPH. Lens of Eye Maximum concentration of NADPH is seen in lens of eye. NADPH is required for preserving the transparency of lens. Macrophage Bactericidal Activity NADPH is required for production of reactive oxygen species (ROS) (superoxide anion radical) by macrophages to kill bacteria. Availability of Ribose Ribose and deoxyribose are required for DNA and RNA synthesis. Ribose is also necessary for nucleotide coenzymes. Reversal of nonoxidative phase is present in all tissues, by which ribose could be made available .

7. REGULATION Cellular Concentration of NADPH Insulin is involved in the regulation of PPP. It enhances the pathway. Disorders Deficiency of G-6-PD Wernicke – Korsakoff syndrome: it is caused by severe deficiency of thiamine. It slows down PPP. It causes memory loss mental confusion and partial paralysis.