Can Gene Expression Regulate Enzymes?

Gene expression in eukaryotes is typically controlled by transcriptional regulators that activate genes encoding structural proteins and enzymes. Most eukaryotes also use small noncoding RNAs to regulate gene expression, such as the enzyme Dicer. Protein degradation is an essential component of gene regulation to meet cellular needs.

Metabolism feeds into the regulation of gene expression via metabolic enzymes and metabolites, which can modulate chromatin directly or indirectly. Six steps at which eucaryotic gene expression can be controlled are discussed in this chapter. Step 6 involves the regulation of protein activity, which includes reversible activation or inactivation by protein.

Cells can control which genes get transcribed and which transcripts get translated, and they can biochemically process transcripts and proteins to affect their activity. This study combines metabolic pulse labelling and absolute quantification of both mRNAs and proteins with mathematical modeling to quantify the major stages of mammalian gene expression. Enzymes are controlled by changes in their conformation, which in turn alter catalytic activity. Genetic control of enzyme activity refers to controlling transcription of the mRNA needed for an enzyme’s synthesis.

Gene expression control is critical to increase production of recombinant proteins, fine-tune metabolic pathways, and reliably express synthetic pathways. Enzymes can be regulated by other molecules that either increase or reduce their activity. In the case of negative control, genes in the operon are expressed unless switched off by a repressor protein.

Are enzymes regulated by gene expression?

Genetic control of enzyme synthesis involves the regulation of the transcription of the mRNA needed for an enzyme’s synthesis. In living cells, hundreds of different enzymes work together in a coordinated manner, requiring precise control mechanisms for turning metabolic reactions on and off. Bacteria use a wide range of mechanisms to regulate enzyme synthesis and activity, with mechanisms for every step between the activation of a gene and the final enzyme reaction from that gene product.

Regulatory proteins in prokaryotic cells can induce, repress, or enhance enzyme synthesis by binding to DNA and either inducing, blocking, or enhancing the function of RNA polymerase, the enzyme required for transcription. These proteins are often part of an operon or a regulon, which are sets of related genes controlled by the same regulatory protein but transcribed as monocistronic units.

Repressors are regulatory proteins that block transcription of mRNA by binding to a portion of DNA called the operator, which lies downstream of a promoter. This binding prevents RNA polymerase from binding to the promoter and transcribing the coding sequence for the enzymes, known as negative control. This is mostly used in biosynthetic reactions where a bacterium only makes a molecule like a particular amino acid when that amino acid is not present in the cell.

How can enzymes be regulated?

Enzymes can be regulated by other molecules that either increase or reduce their activity. Molecules that increase the activity of an enzyme are called activators, while molecules that decrease the activity of an enzyme are called inhibitors.

What does gene expression control?

Gene expression control is critical to increase production of recombinant proteins, fine-tune metabolic pathways and reliably express synthetic pathways. The importance of transcriptional control seems to be most important in eukaryotic systems.

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What is gene expression most commonly regulated by?

Eukaryotic repressors are proteins that regulate gene expression in eukaryotic cells. They bind to specific DNA sequences and inhibit transcription, similar to their prokaryotic counterparts. Some repressors interfere with the binding of other transcription factors to DNA, blocking the interaction of RNA polymerase or general transcription factors with the promoter. Others compete with activators for binding to specific regulatory sequences, with some repressors lacking their activation domain, blocking the binding of the activator.

Active repressors, on the other hand, contain specific functional domains that inhibit transcription via protein-protein interactions. The first active repressor was discovered in 1990 during studies of the gene Krüppel, which is involved in embryonic development in Drosophila. The Krüppel protein contains a discrete repression domain linked to a zinc finger DNA-binding domain, which can be interchanged with distinct DNA-binding domains of other transcription factors. These hybrid molecules also repress transcription, indicating that the Krüppel repression domain inhibits transcription via protein-protein interactions, regardless of its binding site to DNA.

What is the genetic control of enzymes?

Genetic control of enzyme activity is the regulation of enzyme production and activity levels by genes, which dictate the specific properties and functions of an enzyme. This control ensures efficient metabolic reactions and conserves resources. Enzyme induction is an example of genetic control, where the production of a specific enzyme is increased in response to the presence of a substance or inducer molecule. This allows for the efficient breakdown and utilization of certain molecules, such as lactose in the example of the lac operon in E. coli bacteria.

Enzymes, proteins, are synthesized according to the genetic code present in an organism’s DNA. The genes can be active or inactive, leading to an increase or decrease in the production of a specific enzyme. This regulation is crucial for maintaining appropriate levels of enzyme activity within cells, ensuring efficient metabolic reactions and conserving resources. For example, when a cell requires more energy, the genes responsible for synthesis of enzymes involved in energy production may be upregulated, leading to an increase in enzyme production. Conversely, if the cell has enough energy, these genes may be downregulated, resulting in a decrease in enzyme synthesis.

How can control of gene expression occur at the protein level?

By gene expression we mean the transcription of a gene into mRNA and its subsequent translation into protein. Gene expression is primarily controlled at the level of transcription, largely as a result of binding of proteins to specific sites on DNA. In 1965 Francois Jacob, Jacques Monod, and Andre Lwoff shared the Nobel prize in medicine for their work supporting the idea that control of enzyme levels in cells is regulated by transcription of DNA. occurs through regulation of transcription, which can be either induced or repressed. These researchers proposed that production of the enzyme is controlled by an “operon,” which consists a series of related genes on the chromosome consisting of an operator, a promoter, a regulator gene, and structural genes.

• The structural genes contain the code for the proteins products that are to be produced. Regulation of protein production is largely achieved by modulating access of RNA polymerase to the structural gene being transcribed.
• The promoter gene doesn’t encode anything
• it is simply a DNA sequence that is initial binding site for RNA polymerase.
• The operator gene is also non-coding
• it is just a DNA sequence that is the binding site for the repressor.
• The regulator gene codes for synthesis of a repressor molecule that binds to the operator and blocks RNA polymerase from transcribing the structural genes.

The operator gene is the sequence of non-transcribable DNA that is the repressor binding site. There is also a regulator gene, which codes for the synthesis of a repressor molecule hat binds to the operator.

What is the genetic control of enzyme synthesis?

Genetic control of enzyme activity is the regulation of enzyme production and activity levels by genes, which dictate the specific properties and functions of an enzyme. This control ensures efficient metabolic reactions and conserves resources. Enzyme induction is an example of genetic control, where the production of a specific enzyme is increased in response to the presence of a substance or inducer molecule. This allows for the efficient breakdown and utilization of certain molecules, such as lactose in the example of the lac operon in E. coli bacteria.

Enzymes, proteins, are synthesized according to the genetic code present in an organism’s DNA. The genes can be active or inactive, leading to an increase or decrease in the production of a specific enzyme. This regulation is crucial for maintaining appropriate levels of enzyme activity within cells, ensuring efficient metabolic reactions and conserving resources. For example, when a cell requires more energy, the genes responsible for synthesis of enzymes involved in energy production may be upregulated, leading to an increase in enzyme production. Conversely, if the cell has enough energy, these genes may be downregulated, resulting in a decrease in enzyme synthesis.

How is gene expression regulated in biochemistry?

Gene regulation makes cells different. Gene regulation is how a cell controls which genes, out of the many genes in its genome, are “turned on” (expressed). Thanks to gene regulation, each cell type in your body has a different set of active genes—despite the fact that almost all the cells of your body contain the exact same DNA. These different patterns of gene expression cause your various cell types to have different sets of proteins, making each cell type uniquely specialized to do its job.

For example, one of the jobs of the liver is to remove toxic substances like alcohol from the bloodstream. To do this, liver cells express genes encoding subunits (pieces) of an enzyme called alcohol dehydrogenase. This enzyme breaks alcohol down into a non-toxic molecule. The neurons in a person’s brain don’t remove toxins from the body, so they keep these genes unexpressed, or “turned off.” Similarly, the cells of the liver don’t send signals using neurotransmitters, so they keep neurotransmitter genes turned off (Figure 1).

Epigenetic level), when the RNA is transcribed (transcriptional level), when the RNA is processed and exported to the cytoplasm after it is transcribed ( post-transcriptional level), when the RNA is translated into protein (translational level), or after the protein has been made ( post-translational level).

How can enzyme activity be controlled by the cell?

Regulation by Small Molecules. Most enzymes are controlled by changes in their conformation, which in turn alter catalytic activity. In many cases such conformational changes result from the binding of small molecules, such as amino acids or nucleotides, that regulate enzyme activity. This type of regulation commonly is responsible for controlling metabolic pathways by feedback inhibition. For example, the end products of many biosynthetic pathways (e. g., amino acids) inhibit the enzymes that catalyze the first step in their synthesis, thus ensuring an adequate supply of the product while preventing the synthesis of excess amounts ( Figure 7. 33 ).

Figure 7. 33. Feedback inhibition. The end product of a biochemical pathway acts as an allosteric inhibitor of the enzyme that catalyzes the first step in its synthesis.

Feedback inhibition is an example of allosteric regulation, in which a regulatory molecule binds to a site on an enzyme that is distinct from the catalytic site ( allo = “other”; steric = “site”). The binding of such a regulatory molecule alters the conformation of the protein, thereby changing the shape of the catalytic site and affecting catalytic activity (see Figure 2. 29 ). One of the best-studied allosteric enzymes is aspartate transcarbamylase, which catalyzes the first step in the synthesis of pyrimidine nucleotides and is regulated by feedback inhibition by cytidine triphosphate (CTP). Aspartate transcarbamylase consists of 12 distinct polypeptide chains: six catalytic subunits and six regulatory subunits. The binding of CTP to the regulatory subunits induces a major rearrangement of subunit positions, thereby inhibiting enzymatic activity ( Figure 7. 34 ).

How do you regulate an enzymatic pathway?

Substrate availability is a crucial factor in enzyme activity, as substrates bind to enzymes with a characteristic affinity and kinetic parameter called Km. A low substrate concentration results in low enzyme activity, while a high substrate concentration leads to maximal activity. Product inhibition occurs when the product of an enzyme-catalyzed reaction resembles the starting reactant, making it energetically advantageous for the cell if no more product is synthesized. Feedback inhibition is also observed when the end product of an entire pathway can bind to the initial enzyme and inhibit it, allowing the whole pathway to be inhibited.

Allosteric regulation is another important aspect of enzyme activity, as molecules from one pathway can affect the activity of enzymes in another interconnected pathway. Molecules that bind to sites on target enzymes other than the active site can regulate the activity of the target enzyme through conformational changes that can either activate or inhibit its activity.

Phoenic acid changes can alter the conformation of an enzyme and enzyme activity, leading to an alteration in the delicate balance of forces that affect protein structure. Changes in pH can affect the protonation state of key amino acid side chains in the active site of proteins without affecting the local or global conformation of the protein.

Post-translational modifications, such as phosphorylation and dephosphorylation, can affect enzyme activity through local or global shape changes, binding interaction of substrates and allosteric regulators, and even the location of the protein within the cell. Control of phosphorylation state is mediated through signal transduction processes starting at the cell membrane, leading to the activation or inhibition of protein kinases and phosphatases within the cell.

Can proteins affect gene expression?

Gene expression is the process by which the information encoded in a gene is turned into a function. This mostly occurs via the transcription of RNA molecules that code for proteins or non-coding RNA molecules that serve other functions. Gene expression be thought of as an “on/off switch” to control when and where RNA molecules and proteins are made and as a “volume control” to determine how much of those products are made. The process of gene expression is carefully regulated, changing substantially under different conditions and cell types. The RNA and protein products of many genes serve to regulate the expression of other genes. Where, when, and how much a gene is expressed can also assessed by measuring the functional activity of a gene product or observing a phenotype associated with a gene.

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With current technologies, we have the ability to measure mRNA expression of every gene in the entire genome. Sometimes, we can do that in individual cells. This is a really powerful tool to help us measure which genes are turned on, how much and where. Classically, we can also measure gene expression by observing a phenotype or a trait. Examples of those would be to measure a protein activity. If a protein activity can be measured, the gene that encodes for that protein is probably turned on or we can define it as turned on. We can also look for patterns and traits. So for example, if a beautiful butterfly wing with multiple colors is the result of different genes being turned on in different places in the butterfly wing, then we can measure that gene expression simply by observing the wing of the butterfly and marking the locations of the colors.