Pentose Phosphate Pathway

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The pentose phosphate pathway, also known as the hexose monophosphate shunt, is an alternative pathway to glycolysis that helps generate reducing power in the form of NADPH and produces pentose sugars. It occurs in the cytosol in two phases - an oxidative phase that uses NADP+ to produce NADPH and CO2 from glucose-6-phosphate, and a non-oxidative phase that rearranges the pentose sugars to regenerate glucose-6-phosphate and glyceraldehyde-3-phosphate. The NADPH produced is important for biosynthesis of fatty acids and reducing glutathione for antioxidant activity, while the pentose sugars are used for nucleotide and nucleic acid synthesis. Defects

PentosePhosphate Pathway
Dr.SVK Chandrikimath

Introduction
• Alternative route for the metabolism of glucose
• Also known asHexose Monophosphate (HMP)
shunt
• More complex pathway thanglycolysis
• It helpsin
– formation of NADPH for synthesisof fatty acids,
steroids,
– maintaining reduced glutathione forantioxidant
activity
– synthesis of ribose fornucleotide and nucleic acid
formation

Pentose PhosphatePathway
• Likeglycolysis it occurs incytosol
• Oxidation is achieved by dehydrogenation using
NADP+,not NAD+
• Its carried out in 2step:
– Irreversible oxidative phase: 3 molecules of
glucose-6-phosphate give rise to 3 molecules of CO2
and 3 5-carbon sugars.
– Reversible nonoxidative phase: Rearranged to
regenerate 2 molecules of glucose-6 phosphateand
1 molecule of the glyceraldehyde-3phosphate

Oxidativephase
• Dehydrogenation of glucose-6-
phosphate to 6-
phosphogluconate catalyzedby
glucose 6-phosphate
dehydrogenase
• Followed by hydrolysisof
6- phosphogluconolactone to
Ribulose-5-phosphate catalyzed
by 6-phosphogluconate
dehydrogenase
• Decarboxylation follows with
the formation of the
ketopentose ribulose-5-
phosphate
• Both this step requires NADP+as
hydrogenacceptor

Non-oxidativePhase
• Ribulose-5-phosphate is the substrate for two
enzymes
– Ribose-5-phosphate ketoisomerase: ribulose 5-
phosphate to the corresponding ribose-5-
phosphate - used for nucleotide and nucleicacid
synthesis
– Ribulose-5-phosphate 3-epimerase: alters the
configuration about carbon giving xylulose 5-
phosphate

Non-oxidativePhase
• Xylulose-5-phosphate (5c) and Ribose-5-
phosphate (5c) reacts to giveGlyceraldehyde-
3-phosphate (3c) and Sedoheptulose-7-
phosphate (7c) by the enzymeTransketolase
• Glyceraldehyde-3-phosphate (3c) and
Sedoheptulose-7-phosphate (7c) is acted by
Transaldolase to give Fructose-6-phosphate
and Erythrose-4-phosphate

Non-oxidativePhase
• Erythrose-4-phosphate and Xylulose-5-phosphate
reacts in the presence of enzyme Transketolase togive
Fructose-6-phosphate and Glyceraldehyde-3-
phosphate
– Mg 2+and thiamin diphosphate (vitamin B1)ascoenzyme
• Subsequently Fructose-6 –phosphate is isomerisedto
Glucose-6-phosphate by enzyme Phosphohexose
isomerase
• Glyceraldehyde-3-phosphate - reversal of glycolysis
and the gluconeogenic enzyme fructose 1,6
bisphosphatase or itproceeds to glycolysis.

Importance of NADPH
• Bio-synthesis of Fattyacid
• Certain amino acid involving the enzyme
glutamatedehydrogenase
• Antioxidant reaction – Glutathionemediated
reaction of H2O2
• Detoxification of drugs – cytochromeP450
• Phagocytosis
• Integrity of RBCmembrane

Importance of PentoseSugar
• Ribose-5 phosphate – useful for the synthesis
of nucleic acid (RNAand DNA)and nucleotide
• Skeletal muscles capable of synthesizing
pentoses

CLINICAL SIGNIFICANCE
• Genetic defects of glucose-6-phosphate
dehydrogenase
• impairment of the generation of NADPH-X
chromosome
• Mediterranean andAfro-Caribbeanorigin
• red cell hemolysis (hemolyticanemia)
• subjected to oxidativestress
– Infection
– Drugssuchasthe antimalarial primaquine, and
sulfonamides
– Favabeans - favism

The pentose phosphate pathway generates NADPH through two oxidative reactions catalyzed by glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Ribulose-5-phosphate is formed and can undergo reversible nonoxidative reactions to form other pentose and hexose phosphates, including ribose-5-phosphate used for nucleotide biosynthesis. The pathway provides NADPH for processes like glutathione reduction in red blood cells to reduce hydrogen peroxide levels that could otherwise damage red blood cells through oxidative stress. Key enzymes in the oxidative and nonoxidative phases interconvert sugar phosphates to balance NADPH and nucleotide production.

Hmp pathwayKayeen Vadakkan

��

The document summarizes two pathways - the hexose monophosphate (HMP) pathway and the uronic acid pathway. The HMP pathway, also known as the pentose phosphate pathway, generates pentoses and NADPH through oxidative and non-oxidative phases involving multiple enzyme-catalyzed reactions. The uronic acid pathway is an alternative oxidative pathway for glucose that results in the synthesis of glucuronic acid, pentoses, and vitamin C, through a series of four phases including the formation of UDP-glucuronate and its conversion to L-gulonate.

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Pentose phosphate pathwayKayeen Vadakkan

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The document summarizes the pentose phosphate pathway. It consists of an oxidative phase and a non-oxidative phase. The oxidative phase generates NADPH and ribulose 5-phosphate through oxidation reactions. The non-oxidative phase converts ribulose 5-phosphate into other 5-carbon sugars, regenerating glucose 6-phosphate while producing ribose 5-phosphate. The pathway provides reducing power in the form of NADPH for biosynthesis and maintains levels of the antioxidant glutathione.

HMP PATHWAY JubsShrestha

��

HMP shuntabdulrahman amer

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The pentose phosphate pathway generates NADPH and pentose sugars. It has both an oxidative and non-oxidative phase. In the oxidative phase, glucose-6-phosphate is oxidized to produce NADPH. In the non-oxidative phase, 5-carbon sugars are converted into 3 and 6 carbon sugars through a series of isomerization, epimerization, and transketolase reactions. The pathway is important as it provides NADPH for biosynthetic reactions and pentose sugars for nucleotide synthesis. A defect in glucose-6-phosphate dehydrogenase can lead to insufficient NADPH and glutathione, resulting in hemolytic anemia due to oxidative damage of red blood cells.

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1. Glycolysis is a metabolic pathway that converts glucose into pyruvate through a two-phase process requiring 10 enzyme-catalyzed steps. 2. In the preparatory phase, energy is invested to phosphorylate and convert glucose into two molecules of glyceraldehyde-3-phosphate. 3. The payoff phase generates energy as glyceraldehyde-3-phosphate is oxidized and converted to pyruvate, producing a net yield of 2 ATP, 2 NADH, and 2 pyruvate molecules from each original glucose molecule.

Pentose phosphate pathway (Hexose Monophosphate Pathway)Anup Bajracharya

��

Pentose phosphate pathway is an alternative pathway to glycolysis and TCA cycle for oxidation of glucose. It is a shunt of glycolysis. It is also known as hexose monophosphate (HMP) shunt or phosphogluconate pathway. It occurs in cytoplasm of both prokaryotes and eukaryotes. While it involves oxidation of glucose, its primary role is anabolic rather than catabolic. It is an important pathway that generates precursors for nucleotide synthesis and is especially important in red blood cells (erythrocytes).

Pentose phosphate pathway Rajan Kumar

��

The pentose phosphate pathway, also known as the hexose monophosphate shunt, is an alternative metabolic pathway to glycolysis that occurs in the cytosol. It is a complex pathway that helps generate NADPH for fatty acid synthesis and glutathione for antioxidant activity, as well as synthesizing ribose-5-phosphate for nucleotide and nucleic acid formation. Glucose-6-phosphate enters the pathway and is oxidized through a two-phase process involving dehydrogenation using NADP+ instead of NAD+. Several intermediates are formed and rearranged before regenerating glucose-6-phosphate and glyceraldehyde-3-phosphate to complete the nonoxidative phase. Genetic defects in glucose-6

Hexose monophosphate pathway (HMP)HARINATHA REDDY ASWARTHAGARI

��

The document summarizes the hexose monophosphate pathway (HMP pathway), also known as the pentose phosphate pathway. It has two phases - an oxidative phase that generates NADPH, and a non-oxidative phase that converts pentoses to hexoses. The pathway takes place in the cytosol and is important in the liver, red blood cells, and other tissues for generating NADPH for biosynthesis of fatty acids and steroids. It involves the oxidation of glucose-6-phosphate through a series of steps to ultimately regenerate glucose-6-phosphate while producing NADPH and pentose sugars.

PPT4 Hexose monophoshate pathway.pptPharmTecM

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The pentose phosphate pathway consists of an oxidative phase and a non-oxidative phase. In the oxidative phase, glucose-6-phosphate is oxidized to produce ribulose 5-phosphate. The non-oxidative phase then recycles this pentose phosphate back to glucose-6-phosphate using transketolase and transaldolase enzymes. This pathway generates NADPH and pentose phosphates that are used in biosynthesis, with flux controlled by the NADP+ concentration and cell needs.

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Glucose-6-phosphate acts as a branch point for several metabolic pathways. It can be used for glycolysis, glycogen synthesis, the hexose monophosphate shunt, and gluconeogenesis. The hexose monophosphate shunt generates NADPH for biosynthetic reactions through glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. NADPH is required for processes like fatty acid synthesis, cholesterol synthesis, and maintaining reduced glutathione levels in red blood cells. Glucose-6-phosphate dehydrogenase deficiency, which reduces NADPH production, provides some protection against malaria by shortening red blood cell lifespan.

PENTOSE PHOSPHATE PATHWAY.pptxSuganyaPaulraj

��

The pentose phosphate pathway is a metabolic pathway parallel to glycolysis that generates NADPH and pentoses. It occurs mainly in the cytoplasm of liver and red blood cells. Glucose-6-phosphate enters the pathway and undergoes oxidative and non-oxidative reactions. The oxidative reactions produce NADPH, while the non-oxidative reactions produce pentoses and glycolytic intermediates. The overall reaction generates NADPH, CO2, and pentoses from glucose, with NADPH used for lipid and nucleotide biosynthesis and antioxidant defenses.

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The document discusses the hexose monophosphate shunt (HMP shunt), an alternative pathway to glycolysis and the TCA cycle for oxidizing glucose. The HMP shunt occurs in the cytosol and is more anabolic in nature, producing NADPH and pentose through oxidative and non-oxidative phases. Tissues with high HMP shunt activity like the liver, adipose tissue, and lactating mammary glands use the NADPH produced for biosynthesis of fatty acids and steroids.

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The Hexose Monophosphate Shunt (HMP shunt) is an alternative pathway to glucose oxidation that generates NADPH and pentose sugars rather than ATP. It occurs in the cytosol and is most active in tissues involved in lipid and steroid biosynthesis that require NADPH. The pathway has an oxidative phase that produces NADPH and a non-oxidative phase that regenerates pentose sugars. It is important because it provides precursors for nucleic acid synthesis and NADPH for lipid synthesis, steroidogenesis, and antioxidant defenses. Deficiencies in the pathway can cause hemolytic anemia or neurological disorders.

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The pentose phosphate pathway (PPP) has two phases: 1) The oxidative phase generates NADPH and pentoses like ribose-5-phosphate. Glucose-6-phosphate is oxidized to produce NADPH and other intermediates. 2) The non-oxidative phase interconverts pentose phosphates to produce ribose-5-phosphate for nucleotide synthesis. It can also regenerate glycolytic intermediates. The PPP is important because it generates NADPH for biosynthesis of fatty acids, nucleic acids, and protects cells from oxidative damage. It also produces ribose-5-phosphate for nucleotide synthesis. The rate is regulated by NADPH inhibiting glucose-

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The pentose phosphate pathway (PPP), also known as the hexose monophosphate shunt, is an alternative glucose metabolism pathway to glycolysis. It generates NADPH and pentoses through oxidative and non-oxidative phases. NADPH is important for biosynthesis of fatty acids and antioxidation, while pentoses such as ribose-5-phosphate are precursors for nucleic acid synthesis. Certain tissues like liver and red blood cells heavily utilize the PPP. A deficiency in glucose-6-phosphate dehydrogenase, the first enzyme in the oxidative phase, can cause hemolytic anemia upon exposure to oxidative drugs or foods.

GlycolysisAgraniPaudel

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Glycolysis is the breakdown of glucose into pyruvate. It occurs in 10 steps with 2 ATP molecules invested at the start and a net production of 2 ATP and 2 NADH. It is an important pathway as it is common to both aerobic and anaerobic respiration and generates precursors for biosynthesis. Key regulatory enzymes include hexokinase, phosphofructokinase, and pyruvate kinase which are inhibited when energy levels are high.

PENTOSE PHOSPHATE PATHWAY J K COLLEGE,PURULIA

��

The pentose phosphate pathway generates reducing equivalents in the form of NADPH and produces ribose-5-phosphate. It functions primarily in anabolic biosynthesis reactions that require NADPH, such as fatty acid and nucleic acid synthesis. Cells with high levels of these biosynthetic pathways, such as liver, adipose, and lactating mammary gland cells, have high levels of pentose phosphate pathway enzymes. The pathway oxidizes glucose through a series of reactions that ultimately produce ribulose-5-phosphate, which can be converted back into glucose-6-phosphate or other three and six carbon intermediates.

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The document summarizes the pentose phosphate pathway, which has four main purposes: maintaining carbon balance, providing precursors for synthesis of nucleotides and amino acids, producing the reducing agent NADPH, and combating oxidative stress. The pathway occurs in the cytoplasm of nearly all cells, especially liver and red blood cells, and involves both oxidative and non-oxidative stages to produce NADPH, trioses, hexoses, and pentoses from glucose-6-phosphate. Ribulose-5-phosphate produced in this pathway can be converted into other intermediates that re-enter glycolysis or are used for nucleotide synthesis. NADPH produced helps reduce hydrogen peroxide to water through the glutathione system, combating oxidative stress

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Glycolysis and the citric acid cycle (TCA cycle) are two important metabolic pathways. Glycolysis involves 10 steps that convert glucose to pyruvate, producing a small amount of ATP. The TCA cycle further oxidizes pyruvate and acetyl-CoA, producing carbon dioxide, NADH, FADH2, and more ATP. Both pathways occur in the cell's cytoplasm and mitochondria respectively, and are tightly regulated. They are critical for energy production and the synthesis of biomolecules in all living cells.

Unit 2 carbohydrate metabolismYash Institute of Pharmacy, Aurangabad. Maharashtra.

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The document discusses carbohydrate metabolism, specifically glycolysis and the citric acid cycle (TCA cycle). It provides an overview of glycolysis, including its two phases and 10 steps that convert glucose to pyruvate, producing a net of two ATP per glucose molecule. The TCA cycle is summarized as a series of 10 reactions that fully oxidize acetyl-CoA derived from carbohydrates, fats, and proteins, producing carbon dioxide, water, and high-energy electron carriers to fuel oxidative phosphorylation for ATP production. Key regulatory mechanisms and energetics are highlighted for both pathways.

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Glycogen storage diseases are caused by defects in enzymes involved in glycogen metabolism, leading to abnormal glycogen deposition. Von Gierke's disease is caused by glucose-6-phosphatase deficiency, resulting in fasting hypoglycemia, lactic acidosis, hyperlipidemia, and hyperuricemia. The pentose phosphate pathway generates NADPH and pentoses, which are important for lipid, steroid, and nucleic acid synthesis. Glucose-6-phosphate dehydrogenase deficiency can cause hemolytic anemia when exposed to oxidative drugs due to the inability to maintain glutathione levels without NADPH production.

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Pentose Phosphate Pathway

1. PentosePhosphate Pathway Dr.SVK Chandrikimath

2. Introduction • Alternative route for the metabolism of glucose • Also known asHexose Monophosphate (HMP) shunt • More complex pathway thanglycolysis • It helpsin – formation of NADPH for synthesisof fatty acids, steroids, – maintaining reduced glutathione forantioxidant activity – synthesis of ribose fornucleotide and nucleic acid formation

3. Pentose PhosphatePathway • Likeglycolysis it occurs incytosol • Oxidation is achieved by dehydrogenation using NADP+,not NAD+ • Its carried out in 2step: – Irreversible oxidative phase: 3 molecules of glucose-6-phosphate give rise to 3 molecules of CO2 and 3 5-carbon sugars. – Reversible nonoxidative phase: Rearranged to regenerate 2 molecules of glucose-6 phosphateand 1 molecule of the glyceraldehyde-3phosphate

4. Oxidativephase • Dehydrogenation of glucose-6- phosphate to 6- phosphogluconate catalyzedby glucose 6-phosphate dehydrogenase • Followed by hydrolysisof 6- phosphogluconolactone to Ribulose-5-phosphate catalyzed by 6-phosphogluconate dehydrogenase • Decarboxylation follows with the formation of the ketopentose ribulose-5- phosphate • Both this step requires NADP+as hydrogenacceptor

5. Non-oxidativePhase • Ribulose-5-phosphate is the substrate for two enzymes – Ribose-5-phosphate ketoisomerase: ribulose 5- phosphate to the corresponding ribose-5- phosphate - used for nucleotide and nucleicacid synthesis – Ribulose-5-phosphate 3-epimerase: alters the configuration about carbon giving xylulose 5- phosphate

6. Non-oxidativePhase • Xylulose-5-phosphate (5c) and Ribose-5- phosphate (5c) reacts to giveGlyceraldehyde- 3-phosphate (3c) and Sedoheptulose-7- phosphate (7c) by the enzymeTransketolase • Glyceraldehyde-3-phosphate (3c) and Sedoheptulose-7-phosphate (7c) is acted by Transaldolase to give Fructose-6-phosphate and Erythrose-4-phosphate

7. Non-oxidativePhase • Erythrose-4-phosphate and Xylulose-5-phosphate reacts in the presence of enzyme Transketolase togive Fructose-6-phosphate and Glyceraldehyde-3- phosphate – Mg 2+and thiamin diphosphate (vitamin B1)ascoenzyme • Subsequently Fructose-6 –phosphate is isomerisedto Glucose-6-phosphate by enzyme Phosphohexose isomerase • Glyceraldehyde-3-phosphate - reversal of glycolysis and the gluconeogenic enzyme fructose 1,6 bisphosphatase or itproceeds to glycolysis.

9. Importance of NADPH • Bio-synthesis of Fattyacid • Certain amino acid involving the enzyme glutamatedehydrogenase • Antioxidant reaction – Glutathionemediated reaction of H2O2 • Detoxification of drugs – cytochromeP450 • Phagocytosis • Integrity of RBCmembrane

10. Importance of PentoseSugar • Ribose-5 phosphate – useful for the synthesis of nucleic acid (RNAand DNA)and nucleotide • Skeletal muscles capable of synthesizing pentoses

11. CLINICAL SIGNIFICANCE • Genetic defects of glucose-6-phosphate dehydrogenase • impairment of the generation of NADPH-X chromosome • Mediterranean andAfro-Caribbeanorigin • red cell hemolysis (hemolyticanemia) • subjected to oxidativestress – Infection – Drugssuchasthe antimalarial primaquine, and sulfonamides – Favabeans - favism

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Pentose Phosphate Pathway

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