Name: nucleotide building blocks for dna and rna
Uploaded: 2025-06-12T09:38:42.000Z
Duration: 1 min 28 s
Channel: JoVE

Biosynteza kwasów nukleinowych to ściśle regulowany proces, w wyniku którego powstają nukleotydy purynowe i pirymidynowe. Biosynteza puryn rozpoczyna się od rybozo-5-fosforanu, który najpierw przekształca się w pirofosforan fosforybozylu. Konwersja ta prowadzi do powstania monofosforanu inozyny, prekursora monofosforanu adenozyny i monofosforanu guanozyny. Pierścień purynowy powstaje w wyniku pozyskiwania azotu z glutaminy i asparaginianu, podczas gdy atomy węgla są przekazywane przez pochodne glicyny, mrówczanu i kwasu foliowego. Biosynteza pirymidyny przebiega w innej kolejności. Zaczyna się od pierścienia pirymidynowego utworzonego z asparaginianu, glutaminy i wodorowęglanu. Po zbudowaniu tego pierścienia pirofosforan fosforybozylu przekazuje fosforan rybozy, tworząc monofosforan urydyny lub UMP - centralny prekursor nukleotydów pirymidynowych. UMP jest dalej przekształcany w trifosforan cytydyny lub modyfikowany w celu wytworzenia pochodnych tymidyny. Kluczowy mechanizm regulacyjny zapewnia, że synteza zarówno puryn, jak i pirymidyny pozostaje zrównoważona. Hamowanie sprzężenia zwrotnego zapobiega nadmiernej akumulacji nukleotydów, utrzymując homeostazę komórkową.

biosynteza kwasów nukleinowych

Biosynthesis of Nucleic Acids

Biosynteza kwas&#243;w nukleinowych to podstawowy proces biochemiczny, w ramach kt&#243;rego powstaj&#261; nukleotydy purynowe i pirymidynowe niezb&#281;dne do syntezy DNA i RNA. Szlak ten utrzymuje zr&#243;wnowa&#380;on&#261; pul&#281; nukleotyd&#243;w, zapobiegaj&#261;c zaburzeniom, kt&#243;re mog&#322;yby zagrozi&#263; integralno&#347;ci genetycznej i funkcjom kom&#243;rkowym. Z uwagi na kluczowe znaczenie nukleotyd&#243;w ich biosynteza podlega &#347;cis&#322;ej regulacji zapewniaj&#261;cej homeostaz&#281; kom&#243;rkow&#261;.
Biosynteza puryn
Biosynteza nukleotyd&#243;w purynowych rozpoczyna si&#281; od rybozo-5-fosforanu, cukru pentozowego pochodz&#261;cego ze szlaku fosforan&#243;w pentozowych. Rybozo-5-fosforan ulega fosforylacji katalizowanej przez syntetaz&#281; PRPP, tworz&#261;c fosforybozylo-1-pirofosforan (PRPP), b&#281;d&#261;cy aktywowanym substratem. PRPP stanowi rusztowanie, na kt&#243;rym stopniowo powstaje pier&#347;cie&#324; purynowy w szeregu reakcji enzymatycznych.
W tworzeniu pier&#347;cienia purynowego uczestnicz&#261; liczne prekursory: azot z glutaminy i asparaginianu, w&#281;giel z glicyny, formianka (poprzez pochodne tetrahydrofolianu) oraz wodorow&#281;glan. Reakcje te prowadz&#261; do powstania monofosforanu inozyny (IMP), wsp&#243;lnego prekursora monofosforanu adenozyny (AMP) i monofosforanu guanozyny (GMP).
<ul>
<li>Konwersja IMP do AMP wymaga asparaginianu i energii w postaci trifosforanu guanozyny (GTP).</li>
<li>Synteza GMP wymaga glutaminy i energii z adenozynotr&#243;jfosforanu (ATP).</li>
</ul>
Biosynteza pirymidyn
W przeciwie&#324;stwie do biosyntezy puryn, synteza pirymidyn przebiega poprzez wytworzenie zasady azotowej przed przy&#322;&#261;czeniem cukru rybozowego. Pier&#347;cie&#324; pirymidynowy powstaje z asparaginianu, glutaminy i wodorow&#281;glanu jako g&#322;&#243;wnych prekursor&#243;w. Karbamoilofosforanowa syntetaza II (CPSII) katalizuje pierwszy etap szlaku, przekszta&#322;caj&#261;c glutamin&#281; i wodorow&#281;glan do karbamoilofosforanu.
Transkarbamoilaza asparaginianowa do&#322;&#261;cza asparaginian, tworz&#261;c N-karbamoilasparaginian, kt&#243;ry cyklizuje do dihydroorotanu, a nast&#281;pnie utlenia si&#281; do orotanu. Orotan &#322;&#261;czy si&#281; z PRPP, tworz&#261;c monofosforan urydyny (UMP), b&#281;d&#261;cy g&#322;&#243;wnym prekursorem wszystkich nukleotyd&#243;w pirymidynowych.
<ul>
<li>UMP ulega fosforylacji do trifosforanu urydyny (UTP), kt&#243;ry nast&#281;pnie aminowany jest do trifosforanu cytydyny (CTP).</li>
<li>UMP przekszta&#322;cany jest r&#243;wnie&#380; do monofosforanu deoksyurydyny (dUMP), b&#281;d&#261;cego bezpo&#347;rednim prekursorem monofosforanu deoksytymidyny (dTMP). Syntaza tymidylanowa katalizuje t&#281; reakcj&#281;, metyluj&#261;c dUMP z udzia&#322;em N5,N10-metylenotetrahydrofolianu jako donora grupy metylowej.</li>
</ul>
Regulacja biosyntezy nukleotyd&#243;w
Biosynteza nukleotyd&#243;w podlega &#347;cis&#322;ej kontroli poprzez mechanizm inhibicji zwrotnej, kt&#243;ry utrzymuje homeostaz&#281; nukleotydow&#261;. Nagromadzenie ATP, GTP, UTP i CTP wywiera efekt hamuj&#261;cy na kluczowe enzymy szlaku:
<ul>
<li>Syntetaza PRPP i amidotransferaza fosforybozyloglutaminowa, enzymy kluczowe w biosyntezie puryn, s&#261; hamowane przez wysokie st&#281;&#380;enia nukleotyd&#243;w purynowych. </li>
<li>Syntetaza adenylobursztynianowa (szlak syntezy AMP) i dehydrogenaza IMP (szlak syntezy GMP) s&#261; allosterycznie regulowane przez swoje produkty ko&#324;cowe.</li>
<li>CPSII, kluczowy enzym regulacyjny w biosyntezie pirymidyn, jest allosterycznie hamowany przez UTP, a aktywowany przez PRPP i ATP.</li>
<li>Dodatkowo syntetaza CTP, kt&#243;ra przekszta&#322;ca UTP do CTP, jest hamowana przez wysokie st&#281;&#380;enia CTP.</li>
</ul>
Koordynacja mi&#281;dzy biosyntez&#261; puryn a pirymidyn zapewnia zr&#243;wnowa&#380;one zaopatrzenie w nukleotydy do syntezy DNA i RNA, zapobiegaj&#261;c stresowi replikacyjnemu i niestabilno&#347;ci genomowej. Zdolno&#347;&#263; kom&#243;rek do regulacji tych szlak&#243;w ma kluczowe znaczenie dla prawid&#322;owego wzrostu, rozwoju i funkcjonowania kom&#243;rki.
Znaczenie biologiczne
Prawid&#322;owa biosynteza nukleotyd&#243;w jest niezb&#281;dna dla podzia&#322;u kom&#243;rkowego, naprawy DNA oraz ekspresji gen&#243;w. Zaburzenia tych szlak&#243;w mog&#261; prowadzi&#263; do r&#243;&#380;nych stan&#243;w patologicznych:
<ul>
<li>Nowotwory: Niekontrolowana synteza nukleotyd&#243;w to cecha charakterystyczna szybko dziel&#261;cych si&#281; kom&#243;rek nowotworowych. Wiele lek&#243;w przeciwnowotworowych, takich jak antyfoliany (np. metotreksat), dzia&#322;a poprzez hamowanie biosyntezy nukleotyd&#243;w.</li>
<li>Niedobory odporno&#347;ci: Wrodzone defekty metabolizmu puryn, takie jak niedob&#243;r deaminazy adenozynowej (ADA), prowadz&#261; do ci&#281;&#380;kiego z&#322;o&#380;onego niedoboru odporno&#347;ci (SCID).</li>
<li>Zaburzenia neurorozwojowe: zaburzenia metabolizmu nukleotyd&#243;w wi&#261;&#380;&#261; si&#281; z defektami neurorozwojowymi i chorobami mitochondrialnymi.</li>
</ul>
Poprzez z&#322;o&#380;on&#261; regulacj&#281; enzymatyczn&#261; i kontrol&#281; metaboliczn&#261;, biosynteza kwas&#243;w nukleinowych pozostaje fundamentalnym i &#347;ci&#347;le regulowanym procesem w metabolizmie kom&#243;rkowym, zapewniaj&#261;cym stabilno&#347;&#263; genetyczn&#261; i prawid&#322;owe funkcjonowanie kom&#243;rki.

Biosynteza kwasów nukleinowych

Biosynteza kwas&#243;w nukleinowych to podstawowy proces biochemiczny, w ramach kt&#243;rego powstaj&#261; nukleotydy purynowe i pirymidynowe ...

Education

JoVE Core

Microbiology

Mikrobiologia

Unit

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Microbial Metabolism

Metabolizm drobnoustrojów

KEY TERMS AND CONCEPTS

KLUCZOWE TERMINY I POJĘCIA

nucleotide building blocks for dna and rna

Nucleotide biosynthesis makes the building blocks needed for DNA and RNA. Cells use this pathway to make purine and pyrimidine nucleotides and keep their supply balanced. That balance helps protect genetic integrity and supports normal cell function.

Purine nucleotide synthesis starts with ribose-5-phosphate, a sugar made in the pentose phosphate pathway. PRPP synthetase adds phosphate groups to form phosphoribosyl pyrophosphate, or PRPP, which is the activated starting point for the pathway. From there, the purine ring is assembled step by step using nitrogen from glutamine and aspartate, carbon from glycine, formate from tetrahydrofolate derivatives, and bicarbonate.

These reactions produce inosine monophosphate, or IMP. IMP is the common precursor for both adenosine monophosphate, or AMP, and guanosine monophosphate, or GMP. Making AMP requires aspartate and GTP, while making GMP requires glutamine and ATP.

Pyrimidine synthesis follows a different order. The ring is built first, and ribose is attached later. Aspartate, glutamine, and bicarbonate provide the main starting materials. Carbamoyl phosphate synthetase II, or CPSII, carries out the first committed step by making carbamoyl phosphate from glutamine and bicarbonate.

Next, aspartate transcarbamoylase adds aspartate to form N-carbamoyl aspartate. This compound cyclizes into dihydroorotate and then oxidizes to orotate. Orotate then joins PRPP to form uridine monophosphate, or UMP, which is the key precursor for all pyrimidine nucleotides.

UMP can be phosphorylated to form uridine triphosphate, or UTP, and UTP can be aminated to form cytidine triphosphate, or CTP. UMP can also be converted to deoxyuridine monophosphate, or dUMP, which is the direct precursor for deoxythymidine monophosphate, or dTMP. Thymidylate synthase makes this step by methylating dUMP with N5, N10-methylene tetrahydrofolate as the methyl donor.

Cells regulate nucleotide biosynthesis through feedback inhibition. High levels of ATP, GTP, UTP, and CTP can slow the pathway by inhibiting key enzymes. In purine synthesis, PRPP synthetase and glutamine phosphoribosyl amidotransferase are inhibited by high purine nucleotide levels. Adenylosuccinate synthetase and IMP dehydrogenase are also controlled by their products.

Pyrimidine synthesis is regulated in a similar way. CPSII is inhibited by UTP, but it is activated by PRPP and ATP. CTP synthetase, which converts UTP to CTP, is inhibited when CTP levels rise. This coordination between purine and pyrimidine synthesis helps cells keep a steady supply for DNA and RNA production and reduces replication stress and genomic instability.

Proper nucleotide biosynthesis is important for cell division, repair, and gene expression. When these pathways are disrupted, health problems can follow. Uncontrolled nucleotide synthesis is a common feature of rapidly dividing cancer cells, and some chemotherapy drugs, such as methotrexate, target nucleotide biosynthesis to slow cell growth. Defects in purine metabolism, such as adenosine deaminase, or ADA, deficiency, can cause severe combined immunodeficiency, or SCID. Imbalances in nucleotide metabolism are also linked to neurodevelopmental defects and mitochondrial diseases.

Nucleotide Building Blocks for DNA and RNA

nucleotide-building-blocks-for-dna-and-rna

microbial nutrition

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atp and energy production

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ATP is the main energy carrier in cells. It is made of adenosine, which includes adenine and ribose, plus three phosphate groups. The bonds between the phosphate groups hold a large amount of potential energy. When ATP is hydrolyzed, it becomes ADP or AMP and releases energy for cell work. Cells use that energy for many essential tasks. It supports macromolecule synthesis, intracellular transport, and mechanical movement. ATP also acts as an energy manager by linking catabolic and anabolic...

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introduction to metabolism

Metabolism: Energy Use and Biomolecule Synthesis

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Glucose Breakdown and ATP Production

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glycolysis

Glycolysis and Pyruvate Fate

Glycolysis is a central pathway in glucose catabolism and a major way cells make energy. It is also called the Embden-Meyerhof pathway. This process takes place in the cytoplasm and can work with or without oxygen, which makes it useful in many organisms and conditions. Glycolysis has ten steps and turns one glucose molecule into two pyruvate molecules. It has two phases. In the preparatory phase, the cell uses two ATP to add phosphate groups to glucose and split it into two three-carbon...

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Pentose Phosphate Pathway and Entner-Doudoroff

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cellular respiration

Cellular Respiration: ATP Production Pathways

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electron transport chain components

Electron Transport Chain and ATP Production

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chemiosmosis and atp synthesis

Electron Transport Chain Powers ATP Output

The electron transport chain powers ATP production during cellular respiration. It sits in the inner mitochondrial membrane and moves high-energy electrons from NADH and FADH2 to molecular oxygen, the final electron acceptor. As electrons move through the chain, protons are pushed across the membrane to build the gradient needed for ATP synthesis. Electrons from NADH enter the chain at Complex I, also called NADH: ubiquinone oxidoreductase. In prokaryotes, this step helps pump protons from the...

respiration pathways

TCA Cycle and Energy Pathways

Cellular respiration uses the TCA cycle, also called the Krebs cycle, to help cells make usable energy from organic molecules. This pathway is a central part of aerobic respiration and also supports biosynthesis. It links the breakdown of food molecules to the cell's energy needs. Pyruvate from glycolysis enters this process first. The pyruvate dehydrogenase complex converts pyruvate into acetyl-CoA through oxidative decarboxylation. This step produces one NADH and one carbon dioxide molecule.

microbial fermentation

Fermentation Products in Microbes

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metabolism of chemolithotrophs

How Chemolithotrophs Make ATP

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amino acid catabolism

Microbes Use Proteins for Energy

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lipid catabolism

How Microbes Break Down Fats for Energy

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oxygenic photosynthesis

How Plants Make Oxygen and ATP

Oxygenic photosynthesis is the process plants, algae, and cyanobacteria use to capture light energy and turn it into chemical energy. It uses water as the source of electrons and releases molecular oxygen, or O2. The process also produces ATP and NADPH, which cells need for later energy use and carbon fixation. The main reactions happen in the thylakoid membranes, where chlorophyll pigments absorb light. In cyanobacteria, these membranes come from folds in the plasma membrane. Two photosystems...

anoxygenic photosynthesis

Bacterial Light Capture Without Oxygen

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biosynthesis in bacteria

How Bacteria Build Key Macromolecules

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carbon-dioxide fixation

Microbial Carbon Fixation Pathways

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biosynthesis of polysaccharides

Activated Sugars for Polysaccharide Synthesis

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inorganic nitrogen assimilation

Nitrogen Uptake by Microbes

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sulfur assimilation

Sulfur Uptake and Cysteine Synthesis

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amino acid biosynthetic pathways

Amino Acid Building from Cell Metabolites

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biosynthesis of nucleic acids

Nucleotide biosynthesis makes the building blocks needed for DNA and RNA. Cells use this pathway to make purine and pyrimidine nucleotides and keep their supply balanced. That balance helps protect genetic integrity and supports normal cell function. Purine nucleotide synthesis starts with ribose-5-phosphate, a sugar made in the pentose phosphate pathway. PRPP synthetase adds phosphate groups to form phosphoribosyl pyrophosphate, or PRPP, which is the activated starting point for the pathway.

biosynthesis of lipids

How Membrane Lipids Vary Across Life

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formation of lipopolysaccharides

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key terms and concepts

Explore how cells make purine and pyrimidine nucleotides for DNA and RNA, plus the key enzymes, feedback control, and links to disease.

Nucleotide Building Blocks for DNA and RNA | 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

Nucleotide Building Blocks for DNA and RNA

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