tailieunhanh - CHAPTER 5. PENTOSE PHOSPHATE PATHWAY

Two enzymes control the rearrangement of carbon skeletons which result in the production of Glyceraldehyde-3-phosphate and Fructose-6-phosphate. Transketolase transfers C2 units: TPP requiring enzyme like pyruvate dehydrogenase Transaldolase transfers C3 units: uses a shiffs base with an active lysine group | CHAPTER 5. PENTOSE PHOSPHATE PATHWAY INTERNATIONAL UNIVERSITY SCHOOL OF BIOTECHNOLOGY BIOCHEMISTRY Learning objectives To know the enzyme joining the PPP To understand the pathways to form the ribose 5-phosphate To understand the regulation of PPP Content Functions of the pentose phosphate pathway Oxidative reactions leading from glucose 6-phosphate to ribose 5-phosphate Non-oxidative reactions leading to the formation of intermediates of glycolysis FUNCTIONS OF THE PENTOSE PHOSPHATE PATHWAY Provide reduced NADP for synthetic reactions, . fatty acid synthesis and reduction of glutathione Provide pentose phosphate for nucleic acid synthesis Phosphopentose pathway Produces NADPH and ribose-5-phosphate NADH and NADPH although chemically similar they are not metabolically exchangeable. Ratios of [NAD+]/[NADH] ~ 1000 favors metabolite oxidation, whereas ratios of [NADP+]/[NADPH] ~ favors reductive biosynthesis. Many anabolic pathways require the reducing power . | CHAPTER 5. PENTOSE PHOSPHATE PATHWAY INTERNATIONAL UNIVERSITY SCHOOL OF BIOTECHNOLOGY BIOCHEMISTRY Learning objectives To know the enzyme joining the PPP To understand the pathways to form the ribose 5-phosphate To understand the regulation of PPP Content Functions of the pentose phosphate pathway Oxidative reactions leading from glucose 6-phosphate to ribose 5-phosphate Non-oxidative reactions leading to the formation of intermediates of glycolysis FUNCTIONS OF THE PENTOSE PHOSPHATE PATHWAY Provide reduced NADP for synthetic reactions, . fatty acid synthesis and reduction of glutathione Provide pentose phosphate for nucleic acid synthesis Phosphopentose pathway Produces NADPH and ribose-5-phosphate NADH and NADPH although chemically similar they are not metabolically exchangeable. Ratios of [NAD+]/[NADH] ~ 1000 favors metabolite oxidation, whereas ratios of [NADP+]/[NADPH] ~ favors reductive biosynthesis. Many anabolic pathways require the reducing power of NADPH for synthesis including Fatty acid synthesis and the synthesis of cholesterol. 3G-6-P + 6NADP+ + 3H2O 6NADPH + 6H+ 3CO2 + 2F6P + GAP The pathway consists of three parts 1. Oxidative reactions: 3G-6-P + 6NADP+ + 3H2O 6NADPH + 3CO2 + 3Ribulose-5-PO4 2. Isomerization and epimerization reactions: 3Ribulose-5-PO4 Ribose -5-PO4 + 2Xylulose-5-PO4 3. A series of C-C bond cleavage and formations: Ribose-5-PO4 + 2Xyluose-5-PO4 2F-6-P + GAP Glucose-6 phosphate dehydrogenase Phosphogluconate dehydrogenase Ribulose-5-PO4 isomerase Two enzymes control the rearrangement of carbon skeletons which result in the production of Glyceraldehyde-3-phosphate and Fructose-6-phosphate. Transketolase transfers C2 units: TPP requiring enzyme like pyruvate dehydrogenase Transaldolase transfers C3 units: uses a shiffs base with an active lysine group Transketolase requires TPP The transition of carbon skeletons in the Phosphopentose pathway The pentose pathway control