Name: activated sugars for polysaccharide synthesis
Uploaded: 2025-06-12T09:37:21.000Z
Duration: 1 min 26 s
Channel: JoVE

Los polisacáridos, como el glucógeno y el almidón, se sintetizan a partir de nucleósidos difosfato, azúcares como la uridina, difosfato, glucosa (UDPG) o adenosina difosfato glucosa (ADPG). Se produce en un fragmento de polímero preexistente, sirviendo como cebador de elongación de la cadena. Las glucógeno o almidón sintasas extienden estas cadenas añadiendo unidades de glucosa a sus extremos no reductores. La UDPG se forma cuando la glucosa-1-fosfato reacciona con el trifosfato de uridina, catalizado por la UDP-glucosa pirofosforilasa. Los azúcares UDP juegan un papel crucial en la biosíntesis de la pared celular bacteriana. Del mismo modo, el ADPG, sintetizado a partir de glucosa-1-fosfato y trifosfato de adenosina a través de la ADP-pirofosforilasa de glucosa, desempeña un papel clave en la síntesis de glucógeno y almidón. Más allá de la síntesis directa, las células pueden generar glucosa a través de la gluconeogénesis, utilizando fuentes no carbohidratadas como el lactato, los aminoácidos y el glicerol. Esta glucosa se puede convertir en UDPG o ADPG para la biosíntesis de polisacáridos. Estos polisacáridos favorecen la supervivencia microbiana al contribuir a la biosíntesis de la pared celular, el almacenamiento de carbono y la conservación de energía.

biosíntesis de polisacáridos

Biosynthesis of Polysaccharides

Los polisac&#225;ridos como el gluc&#243;geno y el almid&#243;n se sintetizan a partir de az&#250;cares nucle&#243;sido difosfato, principalmente glucosa difosfato de uridina (UDPG) y glucosa difosfato de adenosina (ADPG). Estos donadores de glucosa activados act&#250;an como intermediarios clave en el metabolismo y la bios&#237;ntesis de carbohidratos. La UDPG participa principalmente en la s&#237;ntesis de gluc&#243;geno en animales y muchas bacterias, mientras que la ADPG desempe&#241;a un papel fundamental en la s&#237;ntesis de almid&#243;n en plantas y ciertas bacterias.
La UDPG se forma cuando el fosfato de glucosa-1 reacciona con el trifosfato de uridina (UTP) en una reacci&#243;n catalizada por la UDP-glucosa pirofosforilasa. Esta reacci&#243;n genera un donador de glucosa de alta energ&#237;a que participa en numerosas rutas biosint&#233;ticas. Aunque la UDPG interviene en el metabolismo de carbohidratos, tambi&#233;n act&#250;a como precursor de otros az&#250;cares UDP, incluyendo UDP-N-acetilglucosamina (UDP-GlcNAc) y UDP-N-acetilmur&#225;mico (UDP-MurNAc), esenciales para la bios&#237;ntesis de la pared celular bacteriana.
De manera similar, la ADPG se sintetiza a partir de fosfato de glucosa-1 y ATP a trav&#233;s de la ADP-glucosa pirofosforilasa. Esta enzima es fundamental en la s&#237;ntesis de almid&#243;n en plantas y ciertas bacterias. Una vez formadas, las gluc&#243;geno sintasas o almid&#243;n sintasas a&#241;aden unidades de glucosa a los extremos no reductores de las cadenas de polisac&#225;ridos, alargando su longitud.
El papel de la gluconeog&#233;nesis en la activaci&#243;n de az&#250;cares
Adem&#225;s de la s&#237;ntesis directa a partir de glucosa, las c&#233;lulas pueden generar glucosa mediante gluconeog&#233;nesis, que utiliza precursores no gluc&#237;dicos como lactato, amino&#225;cidos y glicerol. Este proceso es crucial cuando escasean las fuentes externas de glucosa. La ruta invierte la gluc&#243;lisis, con diferencias enzim&#225;ticas clave, permitiendo a la c&#233;lula producir glucosa a partir de intermediarios metab&#243;licos como el fosfoenolpiruvato (PEP). El PEP se sintetiza a partir de oxaloacetato, un intermediario del ciclo del &#225;cido c&#237;trico, y desempe&#241;a un papel central en el metabolismo de carbohidratos en microorganismos.
La gluconeog&#233;nesis comparte etapas con la gluc&#243;lisis, pero utiliza enzimas distintas para sortear reacciones irreversibles. Por ejemplo, el fosfoenolpiruvato carboxiquinasa cataliza la conversi&#243;n de oxaloacetato en fosfoenolpiruvato, mientras que la fructosa bisfosfatasa sustituye a la fosfofructoquinasa-1 (PFK-1) para impulsar la s&#237;ntesis de fructosa-6-fosfato. Una vez sintetizada la glucosa-6-fosfato por gluconeog&#233;nesis, esta act&#250;a como precursor para los az&#250;cares nucle&#243;sido difosfato, alimentando la bios&#237;ntesis de polisac&#225;ridos.
Importancia metab&#243;lica de los az&#250;cares nucle&#243;sido difosfato
Los az&#250;cares nucle&#243;sido difosfato act&#250;an como donadores activados de glucosa, facilitando la s&#237;ntesis de polisac&#225;ridos estructurales y de reserva. La UDPG, por ejemplo, es esencial en la s&#237;ntesis de gluc&#243;geno y sirve como precursor para otros az&#250;cares UDP, incluyendo UDP-galactosa y UDP-&#225;cido glucur&#243;nico, que son fundamentales para la bios&#237;ntesis de la pared celular y en reacciones de glicosilaci&#243;n. Estos az&#250;cares funcionan de manera an&#225;loga al ATP en reacciones de fosforilaci&#243;n, permitiendo la transferencia eficiente de residuos de glucosa en rutas biosint&#233;ticas.
La capacidad de las c&#233;lulas para sintetizar polisac&#225;ridos a partir de az&#250;cares nucle&#243;sido difosfato es crucial para la supervivencia, especialmente en microorganismos que dependen del gluc&#243;geno y el almid&#243;n como reservas de carbono.

Biosíntesis de polisacáridos

Los polisac&#225;ridos como el gluc&#243;geno y el almid&#243;n se sintetizan a partir de az&#250;cares nucle&#243;sido difosfato, principalmente glucosa ...

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Microbial Metabolism

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KEY TERMS AND CONCEPTS

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activated sugars for polysaccharide synthesis

Activated sugars drive polysaccharide synthesis in cells. Glycogen and starch are built from nucleoside diphosphate sugars, mainly uridine diphosphate glucose (UDPG) and adenosine diphosphate glucose (ADPG). These sugar donors act as high-energy intermediates in carbohydrate metabolism and biosynthesis.

UDPG supports glycogen synthesis in animals and many bacteria. It forms when glucose-1-phosphate reacts with uridine triphosphate (UTP). UDP-glucose pyrophosphorylase catalyzes this reaction. UDPG also serves as a precursor for other UDP sugars, including UDP-N-acetylglucosamine (UDP-GlcNAc) and UDP-N-acetylmuramic acid (UDP-MurNAc). These molecules are important for bacterial cell wall biosynthesis.

ADPG has a key role in starch synthesis in plants and some bacteria. It is made from glucose-1-phosphate and ATP by ADP-glucose pyrophosphorylase. After ADPG is formed, glycogen synthases or starch synthases add glucose units to the non-reducing ends of polysaccharide chains. This extends the chain.

Cells can also make glucose through gluconeogenesis when outside glucose is low. Gluconeogenesis uses non-carbohydrate sources such as lactate, amino acids, and glycerol. The pathway runs in reverse direction from glycolysis, but it uses different enzymes to bypass irreversible steps. Phosphoenolpyruvate carboxykinase converts oxaloacetate to phosphoenolpyruvate, and fructose bisphosphatase replaces phosphofructokinase-1 to help form fructose-6-phosphate.

Gluconeogenesis connects to polysaccharide synthesis after glucose-6-phosphate is made. That compound can be turned into nucleoside diphosphate sugars and then used to build storage and structural polysaccharides. In microbial metabolism, phosphoenolpyruvate made from oxaloacetate is an important part of this process.

Nucleoside diphosphate sugars act like activated glucose donors, much like ATP helps drive phosphorylation reactions. UDPG is important not only for glycogen synthesis, but also as a source of UDP-galactose and UDP-glucuronic acid. These sugars support cell wall biosynthesis and glycosylation reactions. This ability to make polysaccharides helps cells survive, especially microorganisms that use glycogen and starch as carbon reserves.

Activated Sugars for Polysaccharide Synthesis

activated-sugars-for-polysaccharide-synthesis

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Activated sugars drive polysaccharide synthesis in cells. Glycogen and starch are built from nucleoside diphosphate sugars, mainly uridine diphosphate glucose (UDPG) and adenosine diphosphate glucose (ADPG). These sugar donors act as high-energy intermediates in carbohydrate metabolism and biosynthesis. UDPG supports glycogen synthesis in animals and many bacteria. It forms when glucose-1-phosphate reacts with uridine triphosphate (UTP). UDP-glucose pyrophosphorylase catalyzes this reaction.

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key terms and concepts

Learn how UDPG and ADPG activate glucose for glycogen and starch synthesis, and how gluconeogenesis supplies precursors for polysaccharide production.

Activated Sugars for Polysaccharide Synthesis | 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

Activated Sugars for Polysaccharide Synthesis

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