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

La vía de las pentosas fosfato funciona simultáneamente con la glucólisis para descomponer las pentosas y la glucosa. En la fase oxidativa, la glucosa-6-fosfato se oxida para generar NADPH, la forma reducida de la coenzima NADP, un agente reductor esencial para la biosíntesis de ácidos nucleicos, ciertos aminoácidos y ácidos grasos. La fase no oxidativa genera ribosa-5-fosfato, un precursor esencial para la síntesis de nucleótidos y ciertos aminoácidos. La vía de las pentosas fosfato no produce ATP directamente, pero los intermedios pueden entrar en glucólisis cuando las bacterias requieren ATP. La vía de Entner-Doudoroff, que se encuentra principalmente en bacterias gramnegativas aerobias, proporciona una alternativa a la glucólisis, produciendo una molécula de piruvato y una molécula de gliceraldehído-3-fosfato. Un mayor catabolismo del gliceraldehído-3-fosfato produce un piruvato adicional. Por cada molécula de glucosa, el EDP produce un ATP, un NADH y un NADPH. Aunque el EDP produce menos ATP que la glucólisis, el NADPH es valioso para las vías biosintéticas.

otras vías glucolíticas

Other Glycolytic Pathways

La ruta de las pentosas fosfato (PPP, por sus siglas en ingl&#233;s) opera en paralelo con la gluc&#243;lisis, facilitando el metabolismo tanto de las pentosas como de la glucosa. Esta v&#237;a consta de dos fases diferenciadas: una fase oxidativa y otra no oxidativa. Aunque no genera ATP de forma directa, los intermediarios formados durante el proceso pueden integrarse en la gluc&#243;lisis, contribuyendo al metabolismo energ&#233;tico celular cuando es necesario.
Fase oxidativa: producci&#243;n de NADPH
La fase oxidativa de la ruta de las pentosas fosfato es principalmente responsable de la generaci&#243;n de fosfato de dinucle&#243;tido de nicotinamida y adenina reducida (NADPH), un agente reductor esencial. En esta fase, la glucosa-6-fosfato experimenta una serie de reacciones enzim&#225;ticas que culminan en la producci&#243;n de ribulosa-5-fosfato. Durante esta conversi&#243;n, se generan dos mol&#233;culas de NADPH por cada mol&#233;cula de glucosa-6-fosfato oxidada. El NADPH desempe&#241;a un papel crucial en reacciones anab&#243;licas, como la bios&#237;ntesis de &#225;cidos nucleicos, amino&#225;cidos y &#225;cidos grasos, as&#237; como en el mantenimiento del equilibrio redox celular mediante la regeneraci&#243;n de glutati&#243;n reducido.
Fase no oxidativa: ribosa-5-fosfato e intermediarios glucol&#237;ticos
La fase no oxidativa de la PPP genera ribosa-5-fosfato, un precursor para la s&#237;ntesis de nucle&#243;tidos y ciertos amino&#225;cidos. Esta fase implica la interconversi&#243;n reversible de fosfatos de az&#250;cares, lo que permite adaptar la ruta a las necesidades metab&#243;licas de la c&#233;lula. Si no se requiere ribosa-5-fosfato para la s&#237;ntesis de nucle&#243;tidos, la ruta redirige los intermediarios carbonados hacia la gluc&#243;lisis mediante reacciones de transcetolasa y transaldolasa, estableciendo as&#237; un v&#237;nculo entre la PPP y el metabolismo central del carbono.
La ruta de Entner-Doudoroff: una alternativa a la gluc&#243;lisis
La ruta de Entner-Doudoroff (EDP, por sus siglas en ingl&#233;s) es una v&#237;a alternativa de catabolismo de la glucosa, presente principalmente en bacterias gramnegativas aerobias como Pseudomonas y Escherichia coli. A diferencia de la gluc&#243;lisis, que comienza con una inversi&#243;n energ&#233;tica de ATP, la EDP omite este paso, descomponiendo la glucosa en una mol&#233;cula de piruvato y otra de gliceraldeh&#237;do-3-fosfato. Esta &#250;ltima contin&#250;a su catabolismo a trav&#233;s de la gluc&#243;lisis, produciendo una mol&#233;cula adicional de piruvato. Este proceso genera una mol&#233;cula de ATP, una de NADH y una de NADPH por cada mol&#233;cula de glucosa metabolizada. Aunque la EDP produce menos ATP en comparaci&#243;n con la gluc&#243;lisis, el NADPH generado es beneficioso para las reacciones biosint&#233;ticas, especialmente en condiciones donde el poder reductor es m&#225;s cr&#237;tico que la generaci&#243;n de ATP.
Flexibilidad metab&#243;lica y funci&#243;n celular
Tanto la ruta de las pentosas fosfato como la ruta de Entner-Doudoroff ilustran la versatilidad metab&#243;lica de las c&#233;lulas bacterianas. La PPP proporciona precursores biosint&#233;ticos esenciales y poder reductor, mientras que la EDP ofrece una v&#237;a alternativa para el metabolismo de la glucosa, especialmente en organismos que carecen de ciertas enzimas glucol&#237;ticas. La integraci&#243;n de estas v&#237;as con la gluc&#243;lisis garantiza que las c&#233;lulas bacterianas puedan adaptarse eficientemente a condiciones variables de nutrientes, optimizando la producci&#243;n de energ&#237;a y la bios&#237;ntesis seg&#250;n sea necesario.

Otras vías glucolíticas

La ruta de las pentosas fosfato (PPP, por sus siglas en ingl&#233;s) opera en paralelo con la gluc&#243;lisis, facilitando el metabolismo tanto de las ...

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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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