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

Der Pentosephosphatweg arbeitet gleichzeitig mit der Glykolyse, um Pentosen und Glukose abzubauen. In der oxidativen Phase wird Glucose-6-phosphat oxidiert, um NADPH zu erzeugen, die reduzierte Form von Coenzym NADP, einem essentiellen Reduktionsmittel für die Biosynthese von Nukleinsäuren, bestimmten Aminosäuren und Fettsäuren. In der nicht-oxidativen Phase entstehen Ribose-5-phosphat, eine essentielle Vorstufe für die Nukleotidsynthese und bestimmte Aminosäuren. Der Pentosephosphat-Weg produziert ATP nicht direkt, aber die Zwischenprodukte können in die Glykolyse eintreten, wenn die Bakterien ATP benötigen. Der Entner-Doudoroff-Signalweg, der hauptsächlich in aeroben gramnegativen Bakterien vorkommt, bietet eine Alternative zur Glykolyse, indem er jeweils ein Molekül Pyruvat und Glycerinaldehyd-3-phosphat produziert. Eine weitere Katabolisierung von Glycerinaldehyd-3-phosphat führt zu einem zusätzlichen Pyruvat. Für jedes Glukosemolekül produziert das EDP ein ATP, ein NADH und ein NADPH. Obwohl EDP weniger ATP produziert als Glykolyse, ist das NADPH wertvoll für Biosynthesewege.

andere glykolytische stoffwechselwege

Other Glycolytic Pathways

Der Pentosephosphatweg (PPP) verl&#228;uft parallel zur Glykolyse und erm&#246;glicht den Metabolismus sowohl von Pentosen als auch von Glucose. Dieser Weg besteht aus zwei klar unterscheidbaren Phasen: der oxidativen und der nicht-oxidativen Phase. Obwohl er nicht direkt ATP generiert, k&#246;nnen die w&#228;hrend des Prozesses gebildeten Intermediate in die Glykolyse eingeschleust werden und so bei Bedarf zum zellul&#228;ren Energiestoffwechsel beitragen.
Oxidative Phase: NADPH-Produktion
Die oxidative Phase des Pentosephosphatwegs ist haupts&#228;chlich f&#252;r die Produktion von Nicotinamidadenindinukleotidphosphat (NADPH), einem essentiellen Reduktionsmittel, verantwortlich. In dieser Phase durchl&#228;uft Glucose-6-phosphat eine Reihe enzymatischer Reaktionen, die in der Bildung von Ribulose-5-phosphat enden. W&#228;hrend dieser Umwandlung entstehen pro oxidiertem Molek&#252;l Glucose-6-phosphat zwei Molek&#252;le NADPH. NADPH spielt eine zentrale Rolle bei anabolen Reaktionen, einschlie&#223;lich der Biosynthese von Nukleins&#228;uren, Aminos&#228;uren und Fetts&#228;uren, sowie bei der Aufrechterhaltung des zellul&#228;ren Redoxgleichgewichts durch die Regeneration von reduziertem Glutathion.
Nicht-oxidative Phase: Ribose-5-Phosphat und glykolytische Intermediate
Die nicht-oxidative Phase des PPP erzeugt Ribose-5-phosphat, ein Vorl&#228;ufer f&#252;r die Synthese von Nukleotiden und bestimmten Aminos&#228;uren. Diese Phase umfasst die reversible Umwandlung von Zuckerphosphaten und erm&#246;glicht so, sich an die metabolischen Bed&#252;rfnisse der Zelle anzupassen. Falls Ribose-5-phosphat nicht f&#252;r die Nukleotidsynthese ben&#246;tigt wird, werden die Kohlenstoffzwischenprodukte &#252;ber Transketolase- und Transaldolase-Reaktionen in die Glykolyse umgeleitet und so der PPP mit dem zentralen Kohlenstoffmetabolismus verkn&#252;pft.
Der Entner-Doudoroff-Weg: Eine Alternative zur Glykolyse
Der Entner-Doudoroff-Weg (EDP) stellt einen alternativen Weg des Glucoseabbaus dar und findet sich haupts&#228;chlich bei aeroben gramnegativen Bakterien wie Pseudomonas und Escherichia coli. Im Gegensatz zur Glykolyse, die mit einer vorbereitenden Investition von ATP beginnt, umgeht der EDP diesen Schritt und spaltet Glucose in je ein Molek&#252;l Pyruvat und Glycerinaldehyd-3-phosphat. Letzteres wird weiter &#252;ber die glykolytische Route abgebaut, wodurch ein zus&#228;tzliches Molek&#252;l Pyruvat entsteht. Dieser Prozess liefert pro metabolisiertem Glucosemolek&#252;l ein Molek&#252;l ATP, ein Molek&#252;l NADH und ein Molek&#252;l NADPH. Obwohl der EDP weniger ATP als die Glykolyse generiert, ist das produzierte NADPH f&#252;r biosynthetische Reaktionen wichtig, insbesondere unter Bedingungen, bei denen die Reduktionskraft wichtiger als die ATP-Erzeugung ist.
Metabolische Flexibilit&#228;t und zellul&#228;re Funktion
Sowohl der Pentosephosphatweg als auch der Entner-Doudoroff-Weg veranschaulichen die metabolische Vielseitigkeit bakterieller Zellen. Der PPP liefert essentielle biosynthetische Vorstufen und Reduktionsmittel, w&#228;hrend der EDP einen alternativen Weg des Glucoseabbaus bietet, insbesondere bei Organismen, denen bestimmte glykolytische Enzyme fehlen. Die Integration dieser Wege mit der Glykolyse gew&#228;hrleistet, dass bakterielle Zellen sich effizient an unterschiedliche N&#228;hrstoffbedingungen anpassen k&#246;nnen, indem sie ihre Energieproduktion und Biosynthese optimal regulieren.

Andere glykolytische Stoffwechselwege

Der Pentosephosphatweg (PPP) verl&#228;uft parallel zur Glykolyse und erm&#246;glicht den Metabolismus sowohl von Pentosen als auch von Glucose. Dieser ...

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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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