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

A via da pentose fosfato opera simultaneamente com a glicólise para quebrar as pentoses e a glicose. Na fase oxidativa, a glicose-6-fosfato é oxidada para gerar NADPH, a forma reduzida da coenzima NADP, um agente redutor essencial para a biossíntese de ácidos nucléicos, certos aminoácidos e ácidos graxos. A fase não oxidativa gera ribose-5-fosfato, um precursor essencial para a síntese de nucleotídeos e certos aminoácidos. A via da pentose fosfato não produz ATP diretamente, mas os intermediários podem entrar na glicólise quando as bactérias precisam de ATP. A via de Entner-Doudoroff, encontrada principalmente em bactérias aeróbicas gram-negativas, fornece uma alternativa à glicólise, produzindo uma molécula de piruvato e gliceraldeído-3-fosfato. O catabolismo adicional do gliceraldeído-3-fosfato produz um piruvato adicional. Para cada molécula de glicose, o EDP produz um ATP, um NADH e um NADPH. Embora o EDP produza menos ATP do que a glicólise, o NADPH é valioso para as vias biossintéticas.

outras vias glicolíticas

Other Glycolytic Pathways

A via das pentoses fosfato (PPP) opera em paralelo &#224; glic&#243;lise, facilitando o metabolismo tanto de pentoses quanto de glicose. Esta via &#233; composta por duas fases distintas: a fase oxidativa e a fase n&#227;o oxidativa. Embora n&#227;o gere ATP diretamente, os intermedi&#225;rios formados durante o processo podem ser integrados &#224; glic&#243;lise, contribuindo para o metabolismo energ&#233;tico celular quando necess&#225;rio.
Fase Oxidativa: Produ&#231;&#227;o de NADPH
A fase oxidativa da via das pentoses fosfato &#233; respons&#225;vel principalmente pela gera&#231;&#227;o de nicotinamida adenina dinucleot&#237;deo fosfato (NADPH), um agente redutor essencial. Nessa fase, a glicose-6-fosfato passa por uma s&#233;rie de rea&#231;&#245;es enzim&#225;ticas, culminando na produ&#231;&#227;o de ribulose-5-fosfato. Durante essa convers&#227;o, duas mol&#233;culas de NADPH s&#227;o produzidas por mol&#233;cula de glicose-6-fosfato oxidada. O NADPH desempenha um papel crucial em rea&#231;&#245;es anab&#243;licas, incluindo a bioss&#237;ntese de &#225;cidos nucleicos, amino&#225;cidos e &#225;cidos graxos, bem como na manuten&#231;&#227;o do equil&#237;brio redox celular ao regenerar o glutationa reduzido.
Fase N&#227;o Oxidativa: Ribose-5-Fosfato e Intermedi&#225;rios Glicol&#237;ticos
A fase n&#227;o oxidativa da PPP gera ribose-5-fosfato, um precursor para a s&#237;ntese de nucleot&#237;deos e de certos amino&#225;cidos. Essa fase envolve a interconvers&#227;o revers&#237;vel de fosfatos de a&#231;&#250;cares, permitindo que a via se adapte &#224;s necessidades metab&#243;licas da c&#233;lula. Se a ribose-5-fosfato n&#227;o for necess&#225;ria para a s&#237;ntese de nucleot&#237;deos, a via redireciona os intermedi&#225;rios de carbono para a glic&#243;lise por meio das rea&#231;&#245;es de transcetolase e transaldolase, conectando a PPP ao metabolismo central do carbono.
A Via de Entner-Doudoroff: Uma Alternativa &#224; Glic&#243;lise
A via de Entner-Doudoroff (EDP) &#233; uma via alternativa de catabolismo da glicose, encontrada principalmente em bact&#233;rias gram-negativas aer&#243;bias, como Pseudomonas e Escherichia coli. Diferentemente da glic&#243;lise, que come&#231;a com um investimento preparat&#243;rio de ATP, a EDP contorna essa etapa, degradando a glicose em uma mol&#233;cula de piruvato e uma de gliceralde&#237;do-3-fosfato. Esta &#250;ltima sofre posterior catabolismo pela via glicol&#237;tica, produzindo uma mol&#233;cula adicional de piruvato. Esse processo gera uma mol&#233;cula de ATP, uma de NADH e uma de NADPH por mol&#233;cula de glicose metabolizada. Embora a EDP produza menos ATP em compara&#231;&#227;o &#224; glic&#243;lise, o NADPH gerado &#233; ben&#233;fico para rea&#231;&#245;es biossint&#233;ticas, especialmente em condi&#231;&#245;es nas quais o poder redutor &#233; mais cr&#237;tico do que a gera&#231;&#227;o de ATP.
Flexibilidade Metab&#243;lica e Fun&#231;&#227;o Celular
Tanto a via das pentoses fosfato quanto a via de Entner-Doudoroff ilustram a versatilidade metab&#243;lica das c&#233;lulas bacterianas. A PPP fornece precursores biossint&#233;ticos essenciais e poder redutor, enquanto a EDP oferece uma rota alternativa para o metabolismo da glicose, particularmente em organismos que carecem de certas enzimas glicol&#237;ticas. A integra&#231;&#227;o dessas vias com a glic&#243;lise assegura que as c&#233;lulas bacterianas possam se adaptar eficientemente a diferentes condi&#231;&#245;es nutricionais, otimizando a produ&#231;&#227;o de energia e a bioss&#237;ntese conforme necess&#225;rio.

Outras Vias Glicolíticas

A via das pentoses fosfato (PPP) opera em paralelo &#224; glic&#243;lise, facilitando o metabolismo tanto de pentoses quanto de glicose. Esta via &#233; ...

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Microbial Metabolism

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KEY TERMS AND CONCEPTS

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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.

microbiology

Pentose Phosphate Pathway and Entner-Doudoroff

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