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pentose phosphate pathway also known as

This will convert Xylulose 5-phosphate into Ribose-5-phosphate and, by transferring unit C2 of the aldose to ketose, will produce glyceraldehyde-3-phosphate and sedoheptulose-7-phosphate. The concentrations of glucose-6-P, NADP+, and NADPH in brain tissue are low (Table 3.2), and the NADP+/NADPH ratio is ~0.01 (Veech et al., 1973). What are the Phases of the Pentose Phosphate Pathway? The HMP shunt is an alternative pathway to glycolysis and is used to produce ribose-5-phosphate and nicotinamide adenine dinucleotide phosphate (NADPH). The nonoxidative branch of the pentose shunt pathway involves interconversion of intermediates via transketolase and transaldolase reactions that can regenerate fructose-6-P and glyceraldehyde-3-P. This phase includes a series of reversible reactions, the direction of which depends on the availability of the substrate. Conversion by phosphopentose isomerase of ribulose-5-P to ribose-6-P forms the precursor for 5-phosphoribosyl-1-pyrophosphate (PRPP), which is the starting point for de novo synthesis of purine ribonucleotides. The latter two build erythrose-4-phosphate and fructose-6-phosphate, catalyzed by transaldolase. When Sedoheptulose-7-Phosphate reacts with Glyceraldehyde-3-Phosphate; it gives 4 carbon compound – Erythrose-4-Phosphate and 6 carbon compound Fructose-6-Phosphate. Pentose phosphate pathway is also known as the ‘hexose monophosphate shunt‘ (HMP) or just shunt pathway, and the ‘phosphogluconate oxidative pathway‘.The pentose phosphate pathway occurs in the cytosol of the cell. Learn how your comment data is processed. Christina Werner, ... Michael Schwarzer, in The Scientist's Guide to Cardiac Metabolism, 2016. The pentose phosphate shunt pathway (Fig. In this pathway glucose-6-phosphate is directly oxidised without entering glycolysis, hence it is also known as Direct Oxidation Pathway or Hexose Monophosphate Shunt. The pentose phosphate pathway (PPP) plays an important role in the synthesis of ribonucleotides and aromatic amino acids. Thus, the four modes of PPP function are shown diagrammatically in Fig. While these are important and universal metabolic pathways, many courses leave out the pentose phosphate pathway (PPP), also known as the hexose monophosphate shunt. Also known as phosphogluconate pathway or the hexose monophosphate shunt, the pentose phosphate pathway (PPP) branches from glycolysis at the first committed step of glucose metabolism. This is the pathway for the synthesis of ribose for nucleotide synthesis (section. R5P is needed for the synthesis of DNA, RNA, ATP, NAD, FAD, CoA, etc… Abbreviations for compounds in the glycolytic pathway are as in Fig. Thus, the predominant function of this pathway is likely to serve different purposes in developing compared to adult brain. The fate of glucose whether to undergo glycolysis or the hexose monophosphate pathway is decided by the relative concentrations of NADP + and NADPH. The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) is a metabolic pathway parallel to glycolysis. Gerald Litwack Ph.D., in Human Biochemistry, 2018. The 6-aminonicotinamide analog of NADP does not participate in hydride transfer reactions (11), and is an exceptionally potent inhibitor of 6-phosphogluconate dehydrogenase (Ki = 1 × 10−7M) (11). The qualitative interconversions that take place are summarized in Figure 14.13, in which stoichiometry is ignored. [2] While the pentose phosphate pathway does involve … Isomerization and epimerization of ribulose-5-phosphate allow the formation of ribose-5-phosphate and xylolose-5-phosphate. The first phase is oxidative and irreversible. Ronald G. Thurman, ... Frederick C. Kauffman, in Microsomes and Drug Oxidations, 1977. The regeneration can be said to involve freeing a two-carbon fragment to combine with a triose to make pentose leaving behind a triose extended by one carbon. It ends thus obtaining two NADPH molecules which, besides their use in reductive biosynthesis, is also responsible for maintaining a reducing environment within the cell. The pentose phosphate pathway (also known as the phosphogluconate pathway or the hexose monophosphate shunt) provides a route by which glucose can be oxidized to carbon dioxide. Hereby, 3-keto 6-phosphogluconate occurs as an unstable intermediate. The concentration of Ribose-5-Phosphate is optimized by the enzyme Glucose-6-Phosphate dehydrogenase in HMP shunt. à Glucose-6-phosphate can be shunted into the pentose-phosphate pathway. HMP also known as the Pentose phosphate pathway. The Pentose Phosphate Pathway maintains cancer’s redox state, but it also a ff ects cell signaling during the cell cycle, as well as managing the metabolic pathways, e.g., xylulose 5-phosphate (see It reconnects with glycolysis because two of the end products of the pentose pathway are glyceraldehyde 3-p and fructose 6-p; two intermediates further down in the glycolytic pathway. Muscle has small amounts of some of the  Pentose Phosphate Pathway enzymes,  because it has little need for synthetic reactions, and therefore, little need for  NADPH. Gluconate-6-phosphate dehydrogenase is also strongly inhibited by NADPH and fructose-2,6-bisphosphate. it is an important pathway for producing NADPH and for interconverting the stereoisomers of carbohydrates. The ratio of NADPH/NADP+ appears to be the principal factor regulating the flux through the pentose phosphate pathway. PPP is regulated oncogenically and/or metabolically by numerous factors, including tumor suppressors, oncoproteins, and intracellular metabolites. Course TitleBIO 361. It is a source of NADPH and ribose-5-Phosphate for nucleic acid biosynthesis. Pentose Phosphate Pathway. 6.26. What is the pentose phosphate pathway important for? The general reaction to this first phase is: Glucose-6-phosphate + 2 NADP + + H 2 O      → Ribulose-5-phosphate + 2 NADPH + 2 H + + CO 2. In the oxidative pentose phosphate pathway, NADPH is formed through the reactions catalyzed by glucose-6-phosphate dehydrogenase and gluconate-6-phosphate dehydrogenase. Alternatively, focus can be put on the transketolase reaction. (NADPH is required for endergonic reductive biosynthesis whereas NADH participates in ATP synthesis via oxidative phosphorylation.) The Hexose Monophosphate Shunt is also known as “Pentose Phosphate Pathway” (PPP). What are … Introduction. NADPH provides reducing power (electron/hydrogen donation ability) for the synthesis of cellular building blocks such as lipids and cholesterol and is also used to produce reduced glutathione, which controls reactive oxygen species (ROS). The products of the pentose phosphate pathway depend critically on cellular requirements because epimerase, isomerase, transketolase- and transaldolase-catalyzed reactions are freely reversible. The pentose phosphate pathway (PPP), also known as the hexose monophosphate (HMP) shunt, occurs in the cytoplasm of all cells, where it serves two major functions: production of NADPH and serving as a source of ribose 5-phosphate for nucleotide synthesis. Like glycolysis, the pentose phosphate pathway happens exclusively in the cytoplasm and it doesn’t require any special organelles which means that all of our cells can use this pathway. It gives Sedoheptulose-7-Phosphate and Glyceraldehyde-3-Phosphate by the enzyme Transketolase. NADPH is a potent competitive inhibitor for the enzyme (Under some conditions). Furthermore, a large substrate reserve for this pathway is present in well-fed animals in the form of glycogen. Pentose phosphate pathway is also known as the ‘hexose monophosphate shunt‘ (HMP) or just shunt pathway, and the ‘phosphogluconate oxidative pathway‘.The pentose phosphate pathway occurs in the cytosol of the cell. Transaldolase deficiency, described in eight patients, was associated with deafness in one patient (Wamelink et al., 2008). Figure 8.4. The pathway uses several steps and different enzymes to achieve this. This latter reaction prepares a central component nucleotide synthesis for the biosynthesis of RNA, DNA and nucleotide cofactors. It was, therefore, of interest to examine the effect of an inhibitor of pentose shunt activity on the kinetics of p-nitrophenol production from p-nitroanisole. Pentose Phosphate Pathway provides Ribose-5-Phosphate for the Purine biosynthesis by the level of Ribose-5-Phosphate is regulated by Glucose-6-Phosphodehydrogenase. Substantial increases in activity of glucose-6-phosphate dehydrogenase have also been observed after ageing of carrot, swede and potato disks. An outline of the pathway is shown in Figure 15.1. In adult brain the flux through the pentose shunt pathway is approximately 5% of the rate of glucose utilization, but brain tissue has a huge excess capacity that is revealed by incubation of brain slices with an artificial electron acceptor, phenazine methosulfate, which stimulates the pathway by 20–50-fold. By continuing you agree to the use of cookies. PPP has two major functions: production of NADPH and making of Ribulose-5-phosphate (R5P). An important function of the NADPH is its role as a cofactor in the glutathione reductase and peroxidase systems to eliminate hydrogen peroxide that is produced by various cellular reactions. This pathway also produces ribose 5-phosphate (R5P), which is required for adenine nucleotide synthesis (Eaton and Brewer, 1974). The hexose monophosphate pathway is used for the production of NADPH from NADP. Pentose phosphate pathway 1. Ribulose-5-Phosphate is isomerized into Ribose-5-Phosphate by the enzyme “Phosphopentose isomerase”. The Pentose Phosphate Pathway (PPP) is one of the key metabolic pathways occurring in living cells to produce energy and maintain cellular homeostasis. Thus, the phase of this non-oxidative metabolic pathway is closed. The pentose phosphate pathway (PPP) is an alternative way of glucose use. No ATP consumed or produced. For this purpose we have employed 6-aminonicotinamide, which is converted into a compound closely resembling NADP. The low rate of this reaction in RBCs occurs because of limited substrate availability (especially NADP+) and because G6PD is strongly inhibited by NADPH and ATP at physiological concentrations (Yoshida, 1973). Joerg Klepper, in Handbook of Clinical Neurology, 2013. The pentose phosphate pathway (PPP), also known as the pentose phosphate shunt, is an important part of glucose metabolism. It is summarized in its connections to other major pathways: glycolysis, glycogen metabolism and the tricarboxylic acid (TCA) cycle in Fig. These last three reactions of the PPP result in two molecules of NADPH. PPP intermediates could also be converted to glyceraldehyde-3-phosphate that returns into the glycolytic pathway, thereby creating a shunt from glucose-6-phosphate that bypasses the initial steps of glycolysis. This reaction is catalyzed by “Phosphopentose Epimerase”. The enzymes for HMP shunt are present in the cytosol of the cell. Ribose is a constituent of RNA, and the related molecule, deoxyribose, is a constituent of DNA. However, this comparatively low enzyme activity does not render sheep RBCs unduly susceptible to the hemolytic effects of oxidant drugs (Maronpot, 1972; Smith, 1968), in part because ATP does not inhibit G6PD in this species (Smith and Anwer, 1971). This metabolic pathway had been discovered through a number of experiments of Lippman, Warburg (1935) and Dickens (1938). The net effect of the metabolism of 3 molecules of G6P through the PPP is as follows (Eaton and Brewer, 1974): G6PD is the rate-limiting reaction in the PPP under physiological conditions. A reduced NADPH/NADP+ ratio should, in principal, signal an increase in cellular demand for NADPH, activation of glucose-6-phosphate dehydrogenase and an increase in the flux through the oxidative pentose phosphate pathway. The pentose phosphate pathway. The pentose phosphate pathway is a metabolic pathway parallel to glycolysis which generates NADPH and pentoses (5-carbon sugars) as well as ribose 5-phosphate. In addition, it is used for the production of ribose for nucleotide and nucleic acid synthesis. It consists of an aerobic and an anaerobic part. The remaining reactions in the PPP are nonoxidative and freely reversible. This reaction is catalyzed by “Transketolase”. This is an alternative Glucose oxidation pathway. Thus the annotation of these two genes is not always correct! Then, again Transketolase enzyme transferring a C2 unit, from Xylulose-5-phosphate to Erythrose-4-phosphate, thus form another molecule of Fructose 6-phosphate and Glyceraldehyde-3-phosphate, both are intermediates of glycolysis. NADPH is utilized to reduce oxidized glutathione to GSH, the substrate for the glutathione peroxidase reaction, and it is bound to catalase, preventing and reversing the accumulation of an inactive form of catalase that is generated when catalase is exposed to H2O2 (Kirkman et al., 1987). The enzymes of the PPP are potential anticancer drug targets, as inhibition of the PPP would reduce nucleotide synthesis and increase ROS-induced cellular damage. How … Pentose phosphate pathway is an alternative route for the oxidation of glucose. The qualitative interconversions that take place are summarized in Figure 14.13, in which stoichiometry is ignored. The pentose phosphate pathway is also called as the phosphogluconate pathway or hexose monophosphate shunt. Fructose‐6‐phosphate, the hexose, is a glycolytic intermediate and can enter that pathway at this stage. 9.7 The Pentose Phosphate Pathway. No molecular analysis and no specific treatments are yet available. The various functions of the PPP can provide NADPH from NAD+ and ribose-5-phosphate for the ultimate synthesis of nucleic acids. Recently patients with single defects in the nonoxidative phase of the pentose phosphate pathway have been discovered. Solution for Q4: Explain in detail ,Why isn't the pentose phosphate pathway very active in muscle tissues compared to adipose tissue? Since pentose shunt flux is stimulated by the addition of aminopyrine (13) and by barbiturate-pretreatment (14), reducing equivalents for mixed-function oxidations have been considered to arise via this pathway. Critically, converting one molecule of glucose to ribulose-5-phosphate during the oxidative phase of the PPP converts two NADP + to two NADPH. As the first enzyme in the PPP (G6PD) is the most common enzymatic deficiency in humans and has few ill effects, the PPP represents a cancer pathway that could be inhibited with limited side effects in normal tissues. 1. Figure 3.6. It is also known as hexose monophosphate shunt (HMP shunt). The 6-carbon glucose (denoted as C6 in a box next to glucose) is converted to a C5 intermediate, which by means of interconversions catalyzed by transketolases and transaldolases, can regenerate C6 and C3 glycolytic intermediates. The pentose phosphate pathway is outlined in Fig. Severe thiamin deficiency affects selective areas of the central nervous system even though all of the enzymes affected are present in all cell types. This reaction proceeds with the utilization of the second glucose molecule. It is here that two free hydrogen ions (proton) and two electrons are transferred to NADP+ which acts as an electron acceptor being reduced to form the first molecule of NADPH; the remaining proton is released in the middle. What is Gluconeogenesis? Control of the chloroplast isoform by the NADPH/NADP+ ratio may therefore be amplified by ribulose-1,5-bisphosphate. About 10% of glucose molecules per day are entering this pathway. G6PD converts glucose-6-phosphate into 6-phosphoglucono-δ-lactone and is the rate-limiting enzyme of this metabolic pathway that supplies reducing energy to cells by maintaining the level of the reduced form of the co-enzyme nicotinamide … Note that SBPases and fructose-1,6-bisphosphatases are related homologous enzymes, that differ by about 75%. However, the relative amount of glucose metabolized in the oxidative pentose phosphate pathway and glycolysis remains unclear. It is the pathway for the formation of pentose sugar. 9.7 The Pentose Phosphate Pathway. About 91% of total NADP is in the reduced form in horse RBCs (Stockham et al., 1994) and 92% to 99% of total NADP is NADPH in human RBCs (Kirkman et al., 1986; Zerez et al., 1987). What is the pentose phosphate pathway also known as? YOU MIGHT ALSO LIKE... ASCP MLT/MLS Certification Exam (BOC) Preparation Its aerobic part leads to ribulose-5-phosphate, carbon dioxide (CO2), and reduced nicotinamide adenine dinucleotide phosphate (NADPH). The pentose shunt pathway is not the only source of NADPH, but it is likely to be the major supplier due to its activation by oxidative stress and exposure to peroxides. At the same time, it carries out the transition to the non-oxidative metabolic phase of the, Pentose Phosphate Pathway producing Biochemical reductant NADPH + H. NADPH involves in Glutathione Reductase catalysis. The first step in the metabolism of glucose through the PPP generates NADPH from the oxidation of G6P in the glucose-6-phosphate dehydrogenase (G6PD) reaction. Treatment of alloxan-diabetic rats with protamine-zinc-insulin for 3 days caused a very marked increase to above normal levels of activity in all the enzymes of the pentose phosphate pathway except ribulose 5-phosphate epimerase, which was restored to the control value. What is the pentose phosphate pathway important for? 3.6). In the Pentose Phosphate Pathway Pathway, few molecules of Glycolytic intermediates are produced these are directly involved in Glycolysis. Figure 5.14 The pentose phosphate pathway (also known as the hexose monophosphate shunt). Note that glucose-6-P can be derived from blood-borne glucose and from glycogen in astrocytes. The Pentose Phosphate Pathway (PPP) is one of the key metabolic pathways occurring in living cells to produce energy and maintain cellular homeostasis. Additionally, the nonoxidative phase of the PPP gives rise to erythrose-4-phosphate, which can contribute to the formation of aromatic amino acids such as phenylalanine, tryptophan, histidine, and tyrosine. Therefore a better understanding of how the PPP is reprogrammed and the mechanism underlying the balance between glycolysis and PPP flux in cancer will be valuable in developing therapeutic strategies targeting this pathway.24, In recent years it has been noticed that the influence of lifestyle, in particular the high-fat Western diet, is associated with the multisite development of cancers. The other mol of xylulose-5-phosphate reacts with the erythrose 4-phosphate, yielding fructose 6-phosphate and glyceraldehyde 3-phosphate. About 10% of glucose molecules per day are entering this pathway. Figure 8.3. Consists of two irreversible oxidative rxs followed by a series of reversible sugar phosphate interconversions. NADH is needed to reduce GSSG (2 glutathione molecules joined by a disulfide bridge; the oxidized form of glutathione) to GSH (glutathione), particularly in cells, such as the red blood cell that are subject to oxidative stresses and the production of H2O2 and free peroxy-radicals. The HMP Shunt, also known as the Pentose Phosphate Pathway or the Phosphogluconate Pathway, is a biochemical pathway that serves as an alternative metabolic pathway for glucose. P.M. Dey, in Plant Biochemistry, 1997. This substrate is oxidized twice by the NADP+-dependent glucose-6-phosphate dehydrogenase to 6-phospho-glucon-δ-lacton as intermediate and by gluconolactonase to 6-phosphogluconate. Glucose-6-phosphate dehydrogenase is also inhibited by ribulose-1,5-bisphosphate. On the contrary, it stimulated p-nitrophenolate production from p-nitoanisole over 2-fold (Table 1). Pentose Phosphate Pathway is the alternative Glucose oxidative pathway. EFFECT OF 6-AMINONICOTINAMIDE PRETREATMENT ON HEPATIC 6-PHOSPHOGLUCONATE CONTENTS. Its aerobic part leads to ribulose-5-phosphate, carbon dioxide (CO2), and reduced nicotinamide adenine dinucleotide phosphate (NADPH). This site uses Akismet to reduce spam. In this reaction, NADP+ acts as a coenzyme. The pentose phosphate pathway is a sequence of events a cell uses to convert a type of glucose into other molecules. Flux through the pentose shunt pathway is also stimulated by addition of catecholamine neurotransmitters to brain slices, presumably due to formation of H2O2 by monoamine oxidase, as well as by exposure of cells to H2O2 or other peroxides that are substrates for glutathione peroxidases (Fig. We use cookies to help provide and enhance our service and tailor content and ads. What are the Steps and Importance of Metabolism? In mode 1, 1 molecule of glucose-6-phosphate (G6P) makes 5 molecules of ribose-5-phosphate (5R5P). The chemical formula of all pentoses is C 5 H 10 O 5, and their molecular weight is 150.13 g/mol.. Pentoses are very important in biochemistry. Glutathione metabolism affects PPP activity via the glutathione reductase (GR) enzyme, which generates NADP as a result of the reduction of GSSG with NADPH (Figure 7.5). Experiments measuring 14CO2 yields and labeling patterns of various intermediates suggest that 5–15% of respiratory glucose metabolism in plant cells proceeds through the oxidative pentose phosphate pathway and will probably not exceed 30% relative to glycolysis. Thomas D. Sharkey, in Reference Module in Life Sciences, 2020. [2] While the pentose phosphate pathway does involve … The pentose phosphate shunt (also known as the hexose monophosphate shunt or the 6-phosphogluconate pathway) shares the intermediates glyceraldehyde-3-phosphate and fructose-6-phosphate with the glycolytic pathway. Whether glucose-6-phosphate enters the oxidative pentose phosphate pathway or the glycolytic pathway in plant cells is critical to our understanding of respiratory glucose metabolism. Role of the Pentose Phosphate Pathway If the oxidation of glucose 6 -phosphate via the pentose phosphate pathway were being used primarily to generate NADPH for biosynthesis, the other product, ribose 5 -phosphate, would accumulate. All SBPase sequences carry a PTS1 suggestive of a glycosomal location, where it probably functions in a modified pentose-phosphate pathway (Hannaert et al., 2003). Six to eight hours following the administration of 6-aminonicotinamide to rats, 6-phosphogluconate levels were elevated approximately 700-fold (Table 2). TABLE 2. Although the pentose phosphate pathway can completely convert glucose-6-phosphate into CO2 (see Fig. Pentose Phosphate Pathway.docx - Pentose Phosphate Pathway... SchoolStony Brook University. What is the pentose phosphate pathway also known as? NADPH is a competitive inhibitor of glucose-6-P DH, indicating that consumption of NADPH and formation of NADP+ provides the required substrate for the reaction which is dependent on continuous supply of glucose-6-P that can be derived from blood-borne glucose or glycogen. Fructose‐6‐phosphate, the hexose, is a glycolytic intermediate and can enter that pathway at this stage. Characteristics of HMP shunt. The first phase is oxidative and irreversible.Glucose-6-phosphate (G6P) is converted via series of steps into Ribulose-5-phosphate.The most important catalytic enzyme is Glucose-6-phosphate Dehydrogenase (G6PD), … Cancer cells have higher cytoplasmic utilization of glucose (glycolysis), even in the presence of oxygen; this is known as the "Warburg Effect". As in the case of glycolysis, the substrate for the pathway is glucose-6-phosphate. The state of chronic positive energy balance is linked to a cluster of conditions, including impaired glucose regulation and insulin resistance, collectively called the metabolic syndrome.25 Hyperglycemia is a distinguishing feature of overnutrition and it is believed to be an independent risk factor for cancer development.26, Z.E. A final reaction of erythrose-4-phosphate and another molecule of xylolose-5-phosphate form fructose-6-phosphate and glycerinaldehyde-3-phosphate, which may directly enter glycolysis. (HMP Shunt). Pentose Phosphate Pathway The pentose phosphate pathway is a metabolic pathway parallel to glycolysis which generates NADPH and pentoses (5-carbon sugars) as well as ribose 5-phosphate. The NADPH is one of the important coenzymes for the microsomal for the liver microsomal, Cytochrome-P450 Mono-Oxygenase system. The pathway begins with the glycolytic intermediate glucose 6-p. Pentose phosphate pathway also called HMP pathway that stands for Hexose Mono- Phosphate Pathway. It has an oxidative phase (NADPH generation) … Sayantan Maitra, ... Pradipta Banerjee, in Nutritional and Therapeutic Interventions for Diabetes and Metabolic Syndrome (Second Edition), 2018, Pentose phosphate pathway (PPP) plays a critical role in regulating cancer cell growth by supplying cells with not only ribose-5-phosphate but also NADPH for detoxification of intracellular ROS, reductive biosynthesis, and ribose biogenesis. In this class, we consider the PPP important for two key reasons. NADPH is necessary for a variety of biosynthetic reactions, some of which are highly active during brain growth and maturation (e.g., lipid biosynthesis) and some that are involved biosynthesis of neuroactive compounds, e.g., nitric oxide synthase, as well as in degradation of catecholamine neurotransmitters (monoamine oxidase). Treatment of alloxan-diabetic rats with protamine-zinc-insulin for 3 days caused a very marked increase to above normal levels of activity in all the enzymes of the pentose phosphate pathway except ribulose 5-phosphate epimerase, which was restored to the control value. The Ki values of NADPH for both enzymes are 11 μM and 20 μM, respectively and the pentose phosphate pathway is therefore regulated by the NADPH/NADP+ ratio. The other mol of xylulose-5-phosphate reacts with the erythrose 4-phosphate, yielding fructose 6-phosphate and glyceraldehyde 3-phosphate. (Guide), VITAMINS : The Micro-Nutrients in Our Body, Phenylketonuria (PKU): What is PKU and its Treatment, Estimation of Blood Glucose level by Folin-Wu method, Assay of Urease Enzyme Activity (Enzymology Practical Protocol), Effect of Temperature on Amylase activity (Enzymology Protocol), Assay of Salivary Amylase enzyme activity, Titration Curve of Glycine: The zwitter ionic changes. PENTOSE PHOSPHATE PATHWAY NILOUFER M.A and Dr. KAYEEN VADAKKAN DEPARTMENT OF BIOTECHNOLOGY ST.MARY’S COLLEGE, THRISSUR 2. The pentose phosphate pathway (PPP) generates NADPH, the major source of reducing equivalents in the protection of RBCs against oxidative injury. Physio Chemical Properties of Amino acids? As shown in Figure 3, the 4‐carbon sugar, erythrose‐4‐phosphate, reacts with a molecule of xylulose‐5‐phosphate, catalyzed by transketolase (2‐carbon transfer): The overall reaction scheme of the pentose phosphate pathway is: In this reaction first and second carbons of Xylulose-5-Phosphate. 3.6). Note that SBPases and fructose-1,6-bisphosphatases are related homologous enzymes, that differ by about 75%. The pentose phosphate pathway occurs in the cytosol and can be divided into two phases: The oxidative portion of the HMP shunt consists of 3 reactions that lead to the formation of Ribulose-5-Phosphate, Carbon dioxide and 2 molecules of NADPH, for each molecule of Glucose-6-Phosphate oxidized. The oxidative component of the pathway generates 2NADPH+2 H+ in successive oxidation reactions starting with glucose-6-P and forming 6-P-gluconate (6PG), then ribulose-5-P (R5P)+CO2. As in the case of glycolysis, the substrate for the pathway is glucose-6-phosphate. In astrocytes, the pentose phosphate shunt pathway is fueled by glucose and glycogen, whereas neurons are dependent on glucose. Making of ribulose-5-phosphate to ribose-5-phosphate is also known as hexose monophosphate pathway 6-phosphogluconate converted! Cells, and the hexose monophosphate shunt Epimerase ” to ribose-5-phosphate is a sequence of events a uses... 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