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

Sulfur is essential for synthesizing amino acids, such as cysteine and methionine, and coenzymes, such as coenzyme A and biotin.Microorganisms absorb sulfur mainly in the form of sulfates from soil and water.Since sulfate is highly oxidized, it must undergo the process of assimilatory sulfur reduction before it is incorporated into biomolecules.This process begins with sulfate activation, catalyzed by ATP sulfurylase, forming adenosine-5-phosphosulfate.This is phosphorylated into 3-phosphoadenosine-5-phosphosulfate or PAPS.PAPS releases sulfite, which is further reduced to hydrogen sulfide by sulfite reductase.In fungi, the hydrogen sulfide combines with serine to form cystine, which is later reduced to cysteine.In bacteria and some archaea, hydrogen sulfide combines with either O-acetylserine or O-phosphoserine to form cysteine.Once formed, cysteine provides sulfur for the synthesis of methionine and other sulfur-containing compounds, such as coenzyme A and biotin.

zwavelassimilatie

Sulfur Assimilation

Zwavel is een essentieel element in biologische systemen en draagt bij aan de synthese van belangrijke biomoleculen, waaronder aminozuren zoals cyste&#239;ne en methionine en cofactoren zoals co-enzym A en biotine. Micro-organismen assimileren zwavel voornamelijk als sulfaat (SO_4^2-) uit de omgeving, dat een reeks biochemische omzettingen moet ondergaan voordat het in cellulaire componenten kan worden opgenomen. Aangezien sulfaat sterk geoxideerd is, moet het een assimilatoire sulfaatreductie ondergaan om biologisch bruikbaar te worden. Sommige micro-organismen kunnen zwavelhoudende aminozuren (cyste&#239;ne, methionine) of gereduceerde zwavelverbindingen (thiosulfaat, elementaire zwavel) gebruiken als alternatieve zwavelbronnen. Deze verbindingen omzeilen de noodzaak van sulfaatactivatie en -reductie, wat een energie-effici&#235;ntere zwavelassimilatie mogelijk maakt.
Sulfaatactivatie en -reductiepad
Het proces begint met de activatie van sulfaat door ATP-sulfurylase, een enzym dat de vorming van adenosine-5&#8242;-fosfosulfaat (APS) katalyseert. APS dient als een cruciaal tussenproduct in het sulfaatmetabolisme en ondergaat ofwel verdere fosforylering tot fosfoadenosine-5&#8242;-fosfosulfaat (PAPS), of gaat in sommige bacteri&#235;n direct over tot reductie. PAPS is niet alleen cruciaal voor zwavelassimilatie, maar ook voor sulfatatiereacties in cellulaire processen.
De reductie van PAPS tot sulfiet (SO_3^2-) vindt plaats via PAPS-reductase, gevolgd door de omzetting van sulfiet tot waterstofsulfide (H_2S) door middel van sulfietreductase. Deze opeenvolgende reducties zetten zwavel om in een biologisch toegankelijke vorm voor organische moleculen. Reductie-equivalenten zoals NADPH doneren elektronen om deze reacties mogelijk te maken.
Incorporatie van waterstofsulfide in cyste&#239;ne
De laatste stap van de zwavelassimilatie omvat de incorporatie van waterstofsulfide in het aminozuurmetabolisme. Bij schimmels reageert (H_2S) met serine om cyste&#239;ne te vormen. Bij bacteri&#235;n en sommige archaea combineert (H_2S) met ofwel O-acetylserine of O-fosfoserine om via enzymatische routes cyste&#239;ne te vormen. O-acetylserine wordt vaker gebruikt in Escherichia coli en verwante bacteri&#235;n, terwijl processen afhankelijk van O-fosfoserine worden aangetroffen in bepaalde archaea, zoals Methanocaldococcus jannaschii.
Cyste&#239;ne is een belangrijke precursor voor de biosynthese van methionine en de productie van zwavelhoudende cofactoren zoals co-enzym A en biotine. Daarnaast speelt het zwavelmetabolisme een rol in de redoxhomeostase, met name via de synthese van glutathion, dat cellen beschermt tegen oxidatieve stress.

Zwavelassimilatie

Zwavel is een essentieel element in biologische systemen en draagt bij aan de synthese van belangrijke biomoleculen, waaronder aminozuren zoals ...

Education

JoVE Core

Microbiology

Microbiologie

Unit

Eenheid

Microbial Metabolism

Microbieel metabolisme

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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

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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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carbon-dioxide fixation

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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

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biosynthesis of nucleic acids

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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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