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

Pentoz fosfat yolu, pentozları ve glikozu parçalamak için glikoliz ile aynı anda çalışır. Oksidatif fazda, glikoz-6-fosfat, nükleik asitlerin, belirli amino asitlerin ve yağ asitlerinin biyosentezi için temel bir indirgeyici ajan olan koenzim NADP'nin indirgenmiş formu olan NADPH'yi üretmek için oksitlenir. Oksidatif olmayan faz, nükleotid sentezi ve belirli amino asitler için önemli bir öncü olan riboz-5-fosfat üretir. Pentoz fosfat yolu doğrudan ATP üretmez, ancak bakteriler ATP'ye ihtiyaç duyduğunda ara ürünler glikolize girebilir. Esas olarak aerobik gram negatif bakterilerde bulunan Entner-Doudoroff yolu, glikolize bir alternatif sağlar ve her biri bir piruvat ve gliseraldehit-3-fosfat molekülü üretir. Gliseraldehit-3-fosfatın daha fazla katabolizması ek bir piruvat verir. EDP, her glikoz molekülü için bir ATP, bir NADH ve bir NADPH üretir. EDP, glikolizden daha az ATP üretse de, NADPH biyosentetik yollar için değerlidir.

diğer glikolitik yollar

Other Glycolytic Pathways

Pentoz fosfat yolu (PPP), glikoliz ile paralel &#231;al&#305;&#351;arak hem pentozlar&#305;n hem de glukozun metabolizmas&#305;n&#305; kolayla&#351;t&#305;r&#305;r. Bu yol, oksidatif ve non-oksidatif olmak &#252;zere iki farkl&#305; a&#351;amadan olu&#351;ur. Do&#287;rudan ATP &#252;retmese de, s&#252;re&#231; s&#305;ras&#305;nda olu&#351;an ara &#252;r&#252;nler glikolize entegre olabilir ve gerekti&#287;inde h&#252;cresel enerji metabolizmas&#305;na katk&#305;da bulunur.
Oksidatif A&#351;ama: NADPH &#220;retimi
Pentoz fosfat yolunun oksidatif a&#351;amas&#305;, esas olarak nikotinamid adenin din&#252;kleotit fosfat (NADPH) &#252;retiminden sorumludur; bu, temel bir indirgeyici ajand&#305;r. Bu a&#351;amada, glukoz-6-fosfat, ribuloz-5-fosfat &#252;retimine yol a&#231;an bir dizi enzimatik reaksiyona u&#287;rar. Bu d&#246;n&#252;&#351;&#252;m s&#305;ras&#305;nda, oksitlenen her glukoz-6-fosfat molek&#252;l&#252; i&#231;in iki NADPH molek&#252;l&#252; &#252;retilir. NADPH, n&#252;kleik asitler, amino asitler ve ya&#287; asitlerinin biyosentezi gibi anabolik reaksiyonlarda ve indirgenmi&#351; glutatyonun yeniden &#252;retilmesiyle h&#252;cresel redoks dengesinin korunmas&#305;nda kritik bir rol oynar.
Non-Oksidatif Evre: Riboz-5-Fosfat ve Glikolitik Ara &#220;r&#252;nler
PPP&#8217;nin non-oksidatif a&#351;amas&#305;, n&#252;kleotid sentezi ve baz&#305; amino asitler i&#231;in bir &#246;nc&#252; olan riboz-5-fosfat &#252;retir. Bu a&#351;ama, &#351;eker fosfatlar&#305;n&#305;n geri d&#246;n&#252;&#351;&#252;ml&#252; kar&#351;&#305;l&#305;kl&#305; d&#246;n&#252;&#351;&#252;m&#252;n&#252; i&#231;erir ve yolun h&#252;crenin metabolik ihtiya&#231;lar&#305;na uyarlanmas&#305;n&#305; sa&#287;lar. E&#287;er riboz-5-fosfat n&#252;kleotid sentezi i&#231;in gerekmiyorsa, transketolaz ve transaldolaz reaksiyonlar&#305; arac&#305;l&#305;&#287;&#305;yla karbon ara &#252;r&#252;nleri glikolize y&#246;nlendirilir ve PPP&#8217;yi merkezi karbon metabolizmas&#305;na ba&#287;lar.
Entner-Doudoroff Yolu: Glikolize Alternatif Bir Yol
Entner-Doudoroff yolu (EDP), &#246;zellikle Pseudomonas ve Escherichia coli gibi aerobik Gram-negatif bakterilerde bulunan alternatif bir glukoz katabolizma yoludur. Glikolizin ATP yat&#305;r&#305;m&#305;na dayal&#305; haz&#305;rl&#305;k a&#351;amas&#305;n&#305; atlayarak, EDP glukozu bir molek&#252;l pir&#252;vat ve bir molek&#252;l gliseraldehit-3-fosfata ay&#305;r&#305;r. &#304;kincisi, glikolitik yol &#252;zerinden daha fazla katabolize edilerek ek bir pir&#252;vat molek&#252;l&#252; &#252;retir. Bu s&#252;re&#231;, metabolize edilen her glukoz molek&#252;l&#252; i&#231;in bir ATP, bir NADH ve bir NADPH &#252;retir. EDP, glikolize k&#305;yasla daha az ATP &#252;retse de, &#252;retilen NADPH, &#246;zellikle indirgeyici g&#252;c&#252;n ATP &#252;retiminden daha kritik oldu&#287;u ko&#351;ullarda biyosentetik reaksiyonlar i&#231;in faydal&#305;d&#305;r.
Metabolik Esneklik ve H&#252;cresel &#304;&#351;lev
Hem pentoz fosfat yolu hem de Entner-Doudoroff yolu, bakteriyel h&#252;crelerin metabolik &#231;ok y&#246;nl&#252;l&#252;&#287;&#252;n&#252; g&#246;sterir. PPP, temel biyosentetik &#246;nc&#252;ller ve indirgeyici g&#252;&#231; sa&#287;larken, EDP, &#246;zellikle baz&#305; glikolitik enzimlere sahip olmayan organizmalarda glikoz metabolizmas&#305; i&#231;in alternatif bir rota sunar. Bu yolaklar&#305;n glikolizle entegrasyonu, bakteriyel h&#252;crelerin de&#287;i&#351;en besin ko&#351;ullar&#305;na verimli bir &#351;ekilde uyum sa&#287;layarak enerji &#252;retimini ve biyosentezi gerekti&#287;i gibi optimize etmesini sa&#287;lar.

Diğer Glikolitik Yollar

Pentoz fosfat yolu (PPP), glikoliz ile paralel &#231;al&#305;&#351;arak hem pentozlar&#305;n hem de glukozun metabolizmas&#305;n&#305; ...

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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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