Name: sulfur uptake and cysteine synthesis
Uploaded: 2025-06-12T09:37:55.000Z
Duration: 1 min 20 s
Channel: JoVE

El azufre es esencial para sintetizar aminoácidos, como la cisteína y la metionina, y coenzimas, como la coenzima A y la biotina. Los microorganismos absorben azufre principalmente en forma de sulfatos del suelo y el agua. Dado que el sulfato está altamente oxidado, debe someterse al proceso de reducción asimiladora del azufre antes de incorporarse a las biomoléculas. Este proceso comienza con la activación del sulfato, catalizado por la ATP sulfurilasa, formando adenosina-5-fosfosulfato. Esto se fosforila en 3-fosfoadenosina-5-fosfosulfato o PAPS. El PAPS libera sulfito, que se reduce aún más a sulfuro de hidrógeno por la sulfito reductasa. En los hongos, el sulfuro de hidrógeno se combina con la serina para formar cistina, que luego se reduce a cisteína. En las bacterias y algunas arqueas, el sulfuro de hidrógeno se combina con O-acetilserina u O-fosfoserina para formar cisteína. Una vez formada, la cisteína proporciona azufre para la síntesis de metionina y otros compuestos que contienen azufre, como la coenzima A y la biotina.

asimilación del azufre

Sulfur Assimilation

El azufre es un elemento esencial en los sistemas biol&#243;gicos, ya que contribuye a la s&#237;ntesis de biomol&#233;culas clave, incluidos amino&#225;cidos como la ciste&#237;na y la metionina, as&#237; como cofactores como la coenzima A y la biotina. Los microorganismos asimilan principalmente el azufre en forma de sulfato (SO_4^2-) del entorno, que debe someterse a una serie de transformaciones bioqu&#237;micas antes de poder incorporarse a los componentes celulares. Dado que el sulfato es una forma altamente oxidada, debe sufrir una reducci&#243;n asimilatoria para volverse biol&#243;gicamente utilizable. Algunos microorganismos pueden utilizar amino&#225;cidos que contienen azufre (ciste&#237;na, metionina) o compuestos de azufre reducido (tiosulfato, azufre elemental) como fuentes alternativas de azufre. Estos compuestos evitan la necesidad de activar y reducir el sulfato, permitiendo una asimilaci&#243;n del azufre m&#225;s eficiente desde el punto de vista energ&#233;tico.
Ruta de activaci&#243;n y reducci&#243;n del sulfato
El proceso comienza con la activaci&#243;n del sulfato por la enzima ATP sulfurilasa, que cataliza la formaci&#243;n de adenosina-5&#8242;-fosfosulfato (APS). El APS act&#250;a como un intermediario clave en el metabolismo del sulfato, pudiendo ser fosforilado adicionalmente para formar fosfoadenosina-5&#8242;-fosfosulfato (PAPS) o bien proceder directamente a la reducci&#243;n en algunas bacterias. El PAPS es crucial no solo para la asimilaci&#243;n del sulfato, sino tambi&#233;n para las reacciones de sulfataci&#243;n en los procesos celulares.
La reducci&#243;n del PAPS a sulfito (SO_3^2-) ocurre mediante la acci&#243;n de la PAPS reductasa, seguida por la conversi&#243;n del sulfito a sulfuro de hidr&#243;geno (H_2S) a trav&#233;s de la sulfito reductasa. Estas reducciones secuenciales convierten el azufre en una forma biol&#243;gicamente accesible para la incorporaci&#243;n en mol&#233;culas org&#225;nicas. Los equivalentes reductores, como el NADPH, donan electrones para facilitar las conversiones en estas reacciones.
Incorporaci&#243;n del sulfuro de hidr&#243;geno a la ciste&#237;na
La etapa final de la asimilaci&#243;n del azufre implica la incorporaci&#243;n del sulfuro de hidr&#243;geno al metabolismo de amino&#225;cidos. En los hongos, el H_2S reacciona con serina para formar ciste&#237;na. En bacterias y algunas arqueas, el H_2S se combina con O-acetilserina o O-fosfoserina para formar ciste&#237;na mediante rutas enzim&#225;ticas. La O-acetilserina es utilizada m&#225;s com&#250;nmente en Escherichia coli y bacterias relacionadas, mientras que las rutas dependientes de O-fosfoserina se encuentran en ciertas arqueas, como Methanocaldococcus jannaschii.
La ciste&#237;na es un precursor clave en la bios&#237;ntesis de metionina y en la producci&#243;n de cofactores que contienen azufre, como la coenzima A y la biotina. Adem&#225;s, el metabolismo del azufre desempe&#241;a un papel importante en la homeostasis redox, particularmente a trav&#233;s de la s&#237;ntesis de glutati&#243;n, que protege a las c&#233;lulas frente al estr&#233;s oxidativo.

Asimilación del Azufre

El azufre es un elemento esencial en los sistemas biol&#243;gicos, ya que contribuye a la s&#237;ntesis de biomol&#233;culas clave, incluidos ...

Education

Educación

JoVE Core

Microbiology

Microbiología

Unit

Unidad

Microbial Metabolism

Metabolismo microbiano

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

sulfur uptake and cysteine synthesis

Sulfur uptake and cysteine synthesis are key parts of microbial metabolism. Sulfur is needed to build important biomolecules, including the amino acids cysteine and methionine, as well as cofactors such as coenzyme A and biotin. Microorganisms usually take in sulfur from the environment as sulfate, but sulfate must be changed before cells can use it.

Because sulfate is highly oxidized, it must go through assimilatory sulfate reduction to become biologically useful. Some microorganisms can also use sulfur-containing amino acids like cysteine and methionine, or reduced sulfur compounds such as thiosulfate and elemental sulfur. These sources bypass sulfate activation and reduction, so they provide a more energy-efficient route for sulfur assimilation.

The pathway starts when ATP sulfurylase activates sulfate and forms adenosine-5′-phosphosulfate, or APS. APS is an important intermediate in sulfate metabolism. In some bacteria, it is reduced directly, while in others it is first phosphorylated to phosphoadenosine-5′-phosphosulfate, or PAPS. PAPS also has a role in sulfation reactions inside cells.

PAPS reductase converts PAPS to sulfite, and sulfite reductase then reduces sulfite to hydrogen sulfide, or H2S. These steps use reducing equivalents such as NADPH to provide electrons. The sequence of reductions turns sulfur into a form that cells can build into organic molecules.

The final step is the use of hydrogen sulfide in amino acid metabolism. In fungi, H2S reacts with serine to form cysteine. In bacteria and some archaea, H2S combines with O-acetylserine or O-phosphoserine to make cysteine. O-acetylserine is common in Escherichia coli and related bacteria, while O-phosphoserine pathways occur in some archaea, including Methanocaldococcus jannaschii.

Cysteine then helps make methionine and sulfur-containing cofactors such as coenzyme A and biotin. Sulfur metabolism also supports redox balance through glutathione synthesis. Glutathione helps protect cells from oxidative stress.

Sulfur Uptake and Cysteine Synthesis

microbial nutrition

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atp and energy production

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introduction to metabolism

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glycolysis

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electron transport chain components

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microbial fermentation

Fermentation Products in Microbes

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metabolism of chemolithotrophs

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Microbes Use Proteins for Energy

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lipid catabolism

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oxygenic photosynthesis

How Plants Make Oxygen and ATP

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Bacterial Light Capture Without Oxygen

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biosynthesis of polysaccharides

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inorganic nitrogen assimilation

Nitrogen Uptake by Microbes

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sulfur assimilation

Sulfur uptake and cysteine synthesis are key parts of microbial metabolism. Sulfur is needed to build important biomolecules, including the amino acids cysteine and methionine, as well as cofactors such as coenzyme A and biotin. Microorganisms usually take in sulfur from the environment as sulfate, but sulfate must be changed before cells can use it. Because sulfate is highly oxidized, it must go through assimilatory sulfate reduction to become biologically useful. Some microorganisms can also...

amino acid biosynthetic pathways

Amino Acid Building from Cell Metabolites

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key terms and concepts

Learn how microbes activate sulfate, reduce it to hydrogen sulfide, and use it to make cysteine, methionine, and sulfur-containing cofactors.

Sulfur Uptake and Cysteine 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

Sulfur Uptake and Cysteine Synthesis

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