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

Nucleic acid biosynthesis is a tightly regulated process that produces purine and pyrimidine nucleotides.&#160;Purine biosynthesis begins with ribose-5-phosphate, first getting converted into phosphoribosyl pyrophosphate.This conversion leads to the formation of inosine monophosphate, a precursor to adenosine monophosphate and guanosine monophosphate.The purine ring is formed by deriving nitrogen from glutamine and aspartate, while carbon atoms are donated by glycine, formate, and folate derivatives.Pyrimidine biosynthesis follows a different sequence.It starts with a pyrimidine ring formed from aspartate, glutamine, and bicarbonate.Once this ring is built, phosphoribosyl pyrophosphate donates a ribose-phosphate, forming uridine monophosphate or UMP &#8212;the central precursor for pyrimidine nucleotides.UMP is further converted into cytidine triphosphate or modified to generate thymidine derivatives.A key regulatory mechanism ensures that both purine and pyrimidine synthesis remain balanced.Feedback inhibition prevents the excessive accumulation of nucleotides, maintaining cellular homeostasis.

biosynthesis of nucleic acids

Biosynthesis of Nucleic Acids

Nucleic acid biosynthesis is a fundamental biochemical process that produces the purine and pyrimidine nucleotides essential for DNA and RNA synthesis. This pathway maintains a balanced nucleotide pool, preventing imbalances that could jeopardize genetic integrity and cellular function. Given the crucial role of nucleotides, their synthesis is tightly regulated to ensure proper cellular homeostasis.Purine BiosynthesisThe biosynthesis of purine nucleotides begins with ribose-5-phosphate, a pentose sugar derived from the pentose phosphate pathway. Ribose-5-phosphate undergoes phosphorylation by PRPP synthetase to form phosphoribosyl pyrophosphate (PRPP), a key activated substrate. PRPP is the foundation upon which the purine ring is gradually assembled through a series of enzymatic reactions.Multiple precursors contribute to the purine ring: nitrogen from glutamine and aspartate, carbon from glycine, formate (via tetrahydrofolate derivatives), and bicarbonate. The sequential reactions lead to the formation of inosine monophosphate (IMP), the common precursor for both adenosine monophosphate (AMP) and guanosine monophosphate (GMP).<ul><li>Conversion of IMP to AMP requires aspartate and guanosine triphosphate (GTP) energy.</li><li>The synthesis of GMP requires glutamine and energy from adenosine triphosphate (ATP).</li></ul>Pyrimidine BiosynthesisIn contrast to purine biosynthesis, pyrimidine synthesis builds the nitrogenous base first before attaching it to the ribose sugar. The pyrimidine ring uses aspartate, glutamine, and bicarbonate as primary precursors. Carbamoyl phosphate synthetase II (CPSII) catalyzes the first committed step by converting glutamine and bicarbonate into carbamoyl phosphate.Aspartate transcarbamoylase then incorporates aspartate to form N-carbamoyl aspartate, which cyclizes into dihydroorotate before oxidizing to produce orotate. Orotate is then linked to PRPP, forming uridine monophosphate (UMP), the pivotal precursor for all pyrimidine nucleotides.<ul><li>UMP is phosphorylated to form uridine triphosphate (UTP), further aminated to cytidine triphosphate (CTP).</li><li>UMP is also converted into deoxyuridine monophosphate (dUMP), the direct precursor for deoxythymidine monophosphate (dTMP). Thymidylate synthase catalyzes this reaction, which methylates dUMP using N5, N10-methylene tetrahydrofolate as a methyl donor.</li></ul>Regulation of Nucleotide BiosynthesisBiosynthesis is tightly regulated through feedback inhibition to maintain nucleotide homeostasis. The accumulation of ATP, GTP, UTP, and CTP exerts inhibitory effects on key enzymes within the pathway:<ul><li>PRPP synthetase and glutamine phosphoribosyl amidotransferase, crucial enzymes in purine biosynthesis, are inhibited by high levels of purine nucleotides.</li><li>Adenylosuccinate synthetase (in the AMP synthesis pathway) and IMP dehydrogenase (in the GMP synthesis pathway) are also allosterically regulated by their respective nucleotide products.</li><li>CPSII, a key regulatory enzyme in pyrimidine biosynthesis, is allosterically inhibited by UTP while being activated by PRPP and ATP.</li><li>Additionally, CTP synthetase, which converts UTP to CTP, is inhibited by high CTP levels.</li></ul>The coordination between purine and pyrimidine biosynthesis ensures a balanced nucleotide supply for DNA and RNA synthesis, preventing replication stress and genomic instability. The ability of cells to regulate these pathways is crucial for normal growth, development, and cellular function.Biological ImplicationsProper nucleotide biosynthesis is essential for cell division, repair, and gene expression. Disruptions in these pathways can lead to various pathological conditions:<ul><li>Cancer: Uncontrolled nucleotide synthesis is a hallmark of rapidly dividing cancer cells. Many chemotherapy drugs, such as antifolates (e.g., methotrexate), target nucleotide biosynthesis to inhibit cancer cell proliferation.</li><li>Immunodeficiency Disorders: Genetic defects in purine metabolism, such as adenosine deaminase (ADA) deficiency, result in severe combined immunodeficiency (SCID).</li><li>Neurodevelopmental Disorders: Imbalances in nucleotide metabolism are linked to neurodevelopmental defects and mitochondrial diseases.</li></ul>Through intricate enzymatic regulation and metabolic control, nucleic acid biosynthesis remains an essential and highly controlled process in cellular metabolism, ensuring genetic stability and proper cellular function.

Nucleic acid biosynthesis is a fundamental biochemical process that produces the purine and pyrimidine nucleotides essential for DNA and RNA synthesis. ...

Education

JoVE Core

Microbiology

Unit

Microbial Metabolism

KEY TERMS AND CONCEPTS

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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Fermentation Products in Microbes

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How Chemolithotrophs Make ATP

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Microbes Use Proteins for Energy

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carbon-dioxide fixation

Microbial Carbon Fixation Pathways

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Activated Sugars for Polysaccharide Synthesis

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Nitrogen Uptake by Microbes

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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.

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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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