Name: pentose phosphate pathway and entner-doudoroff
Uploaded: 2025-06-12T09:33:57.000Z
Duration: 1 min 24 s
Channel: JoVE

The pentose phosphate pathway operates simultaneously with glycolysis to break down pentoses and glucose.In the oxidative phase, glucose-6-phosphate is oxidized to generate NADPH, the reduced form of coenzyme NADP, an essential reducing agent for the biosynthesis of nucleic acids, certain amino acids, and fatty acids.The non-oxidative phase generates ribose-5-phosphate, an essential precursor for nucleotide synthesis and certain amino acids.The pentose phosphate pathway does not directly produce ATP, but the intermediates can enter glycolysis when the bacteria require ATP.The Entner-Doudoroff pathway, primarily found in aerobic gram-negative bacteria, provides an alternative to glycolysis, producing one molecule each of pyruvate and glyceraldehyde-3-phosphate.Further catabolism of glyceraldehyde-3-phosphate yields an additional pyruvate.For each glucose molecule, the EDP produces one ATP, one NADH, and one NADPH.Though EDP produces less ATP than glycolysis, the NADPH is valuable for biosynthetic pathways.

andere glycolytische routes

Other Glycolytic Pathways

De pentose phosphate pathway (PPP) gaat parallel aan de glycolyse en begeleidt de afbraak van zowel pentosen als glucose. Dit proces bestaat uit twee afzonderlijke fasen: de oxidatieve en de niet-oxidatieve fase. Hoewel het proces geen ATP produceert, kunnen de gevormde tussenproducten worden ge&#239;ntegreerd in de glycolyse en zo bijdragen aan het cellulaire energiemetabolisme wanneer nodig.
Oxidatieve Fase: NADPH-productie
De oxidatieve fase van het pentosefosfaatproces is voornamelijk verantwoordelijk voor de productie van nicotinamide-adenine-dinucleotidefosfaat (NADPH), een onmisbare reducerende stof. In deze fase ondergaat glucose-6-fosfaat een reeks enzymatische reacties die uiteindelijk leiden tot de vorming van ribulose-5-fosfaat. Tijdens deze omzetting worden twee moleculen NADPH geproduceerd per geoxideerd molecuul glucose-6-fosfaat. NADPH speelt een cruciale rol in anabole reacties, waaronder de biosynthese van nucle&#239;nezuren, aminozuren en vetzuren, evenals in het handhaven van de cellulaire redoxbalans door regeneratie van gereduceerde glutathion.
Niet-Oxidatieve Fase: Ribose-5-Fosfaat en Glycolytische Tussenproducten
De niet-oxidatieve fase van het PPP produceert ribose-5-fosfaat, een voorloper voor de synthese van nucleotiden en bepaalde aminozuren. Deze fase omvat de omkeerbare interconversie van suikerfosfaten, waardoor het pad zich kan aanpassen aan de metabole behoeften van de cel. Indien ribose-5-fosfaat niet nodig is voor de nucleotidensynthese, worden de koolstofintermediairs via transketolase- en transaldolase-reacties omgeleid naar de glycolyse, wat een koppeling vormt tussen het PPP en de centrale koolstofstofwisseling. 
De Entner-Doudoroff Pathway: Een Alternatief voor Glycolyse
De Entner-Doudoroff Pathway (EDP) is een alternatief pad voor het katabolisme van glucose, dat voornamelijk voorkomt bij aerobe gramnegatieve bacteri&#235;n zoals Pseudomonas en Escherichia coli. In tegenstelling tot de glycolyse, die begint met een voorbereidende investering van ATP, slaat de EDP deze stap over en breekt glucose af tot &#233;&#233;n molecuul pyruvaat en &#233;&#233;n molecuul glyceraldehyde-3-fosfaat. Deze ondergaat verdere afbraak via het glycolytische pad, wat resulteert in een extra pyruvaatmolecuul. Dit proces levert &#233;&#233;n ATP, &#233;&#233;n NADH en &#233;&#233;n NADPH per gemetaboliseerd glucosemolecuul. Hoewel de EDP minder ATP produceert dan de glycolyse, is de geproduceerde NADPH voordelig voor biosynthetische reacties, vooral onder omstandigheden waarin reductiekracht belangrijker is dan ATP-productie.
Metabole Flexibiliteit en Celfunctie
Zowel de pentose phosphate pathway en de Entner-Doudoroff pathway illustreren de metabole veelzijdigheid van bacteri&#235;le cellen. De PPP levert essenti&#235;le biosynthetische voorlopers en reducerende kracht, terwijl de EDP een alternatief pad biedt voor glucosemetabolisme, vooral bij organismen die bepaalde glycolytische enzymen missen. De integratie van deze routes met de glycolyse zorgt ervoor dat bacteri&#235;le cellen zich effici&#235;nt kunnen aanpassen aan wisselende voedingsstofcondities en zo de energieproductie en biosynthese kunnen optimaliseren naargelang waar nodig.

Andere Glycolytische Routes

De pentose phosphate pathway (PPP) gaat parallel aan de glycolyse en begeleidt de afbraak van zowel pentosen als glucose. Dit proces bestaat uit twee ...

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pentose phosphate pathway and entner-doudoroff

The pentose phosphate pathway works alongside glycolysis in cells that need both sugar breakdown and building blocks for growth. It handles pentoses, which are five-carbon sugars, and also uses glucose as a starting point. The pathway has two parts, an oxidative phase and a non-oxidative phase. It does not make ATP directly, but its products can feed back into glycolysis when the cell needs them.

The oxidative phase mainly makes NADPH, a reduced electron carrier. In this phase, glucose-6-phosphate goes through several enzyme steps and becomes ribulose-5-phosphate. Two NADPH molecules are produced from each glucose-6-phosphate that is oxidized. NADPH is important for building nucleic acids, amino acids, and fatty acids, and it also helps keep the cell in redox balance by regenerating reduced glutathione.

The non-oxidative phase makes ribose-5-phosphate, which cells use to build nucleotides. It also supports the production of certain amino acids. This phase uses reversible reactions that move sugar phosphates between forms, so the pathway can match the cell’s current needs. If ribose-5-phosphate is not needed for nucleotide synthesis, carbon intermediates are sent into glycolysis through transketolase and transaldolase reactions.

The Entner-Doudoroff pathway is another way to break down glucose. It is found mainly in aerobic gram-negative bacteria such as Pseudomonas and Escherichia coli. Unlike glycolysis, it skips the ATP investment step at the start. Glucose is split into one pyruvate and one glyceraldehyde-3-phosphate, and the glyceraldehyde-3-phosphate is then processed through glycolysis to make a second pyruvate.

This pathway makes one ATP, one NADH, and one NADPH per glucose molecule. That is less ATP than glycolysis, but the NADPH can be useful for biosynthesis. It matters most when a cell needs reducing power more than ATP. Together, the pentose phosphate pathway and the Entner-Doudoroff pathway show how bacteria can adjust metabolism to fit changing nutrient conditions and support both energy use and biosynthesis.

Pentose Phosphate Pathway and Entner-Doudoroff

pentose-phosphate-pathway-and-entner-doudoroff

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The pentose phosphate pathway works alongside glycolysis in cells that need both sugar breakdown and building blocks for growth. It handles pentoses, which are five-carbon sugars, and also uses glucose as a starting point. The pathway has two parts, an oxidative phase and a non-oxidative phase. It does not make ATP directly, but its products can feed back into glycolysis when the cell needs them. The oxidative phase mainly makes NADPH, a reduced electron carrier. In this phase,...

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key terms and concepts

Learn how the pentose phosphate pathway makes NADPH and ribose-5-phosphate, and how the Entner-Doudoroff pathway helps bacteria metabolize glucose.

Pentose Phosphate Pathway and Entner-Doudoroff | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

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Pentose Phosphate Pathway and Entner-Doudoroff

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