4.5.4. Regulation of enzyme activity

Regulation of enzyme activity

The rate of enzymatic reactions depends on a number of factors, including the following:

Influence of temperature

If we supply energy in the form of heat to an enzymatic reaction, when it is captured by the molecules it is transformed into kinetic energy. In this way, the movement of the molecules and the number of intermolecular encounters increases. Thus, increasing the temperature increases the speed of chemical reactions.

If the temperature is too high, the enzyme loses its tertiary structure, becomes denatured and ceases to be functional. There is an optimal temperature for which the enzymatic activity is maximum.

If you decrease the temperature, the activity also decreases, but the enzyme is not destroyed, and the process is reversible.

Influence of pH

All enzymes have an optimal pH at which they are most effective, although they can function between two pH limit values. If the pH is outside these limits, the enzyme denatures and stops working.

Influence of substrate concentration

If you increase the substrate concentration, keeping the enzyme concentration constant , the rate of the reaction increases. As there are more substrate molecules, the enzyme-substrate encounter is more likely to occur.

This increase in speed has a limit, since if the substrate concentration is excessive, all enzymes will be in the ES complex form, they will be saturated, and the reaction speed will not increase.

If the substrate concentration is decreased, the rate of the chemical reaction will decrease.

Activators effect

There are some ions that favor the binding between the enzyme and the substrate. For example, the enzyme phosphorylase is activated by the presence of magnesium ions Mg²⁺, forming ATP from ADP and a phosphate group (H₃PO₄).

Effect of inhibitors

Inhibitors are substances that decrease the activity and effectiveness of an enzyme or completely prevent its action. Inhibition can be of two types: irreversible and reversible.

The irreversible inhibition or poisoning of the enzyme occurs when the inhibitor is permanently fixed to the active site of the enzyme by altering their structure and thus making it unusable.
The reversible inhibition occurs when temporarily prevents normal operation of the enzyme without disabling the active center. There are two ways: competitive and non- competitive.
- The reversible inhibition competitive occurs when the inhibitor is similar to the substrate, so that both can bind to the active center of the enzyme.
  - If the substrate is attached to the enzyme, the products are formed.
  - If the inhibitor is fixed, the enzyme cannot act until it is released from the inhibitor.
- The reversible inhibition noncompetitive is due to an inhibitor that binds to the enzyme by a different site to which the substrate does, by altering its conformation. It can also act on the enzyme-substrate complex, making it fixed.

A special case of inhibition is uncompetitive inhibition, in which the inhibitor does not bind to the free enzyme, but to the enzyme-substrate complex to prevent product formation.

Fundamental insights on the regulation of enzyme activity

The speed of enzymatic reactions depends on several factors:

Influence of temperature.
As the temperature increases to an optimum temperature, the molecules move faster and the number of encounters between molecules is greater, thus increasing the speed of the reaction. If the temperature continues to increase, the formation of the enzyme-substrate complex becomes more difficult and the reaction speed decreases, in addition to the denaturation of the enzyme and the loss of its functionality, since it loses its secondary, tertiary structures (mainly) and quaternary.

The denaturation is usually irrerversible, although again lower the temperature, the enzyme does not recover its native three - dimensional structure. Sometimes, if it has been subjected to denaturing factors and low intensity for a short time, denaturation can be reversible.
Influence of pH.
- Each enzyme has its maximum activity (maximum reaction rate) at a certain pH called the optimum pH. Outside this pH, the structure of the enzyme is altered and its catalytic capacity is less effective.
Influence of the substrate concentration.
- As the concentration of substrate increases, if the concentration of the enzyme does not vary, it is more likely that encounters between enzymes and substrates will occur, thus the reaction rate increases.
- If the substrate concentration is excessive, all the enzymes will be saturated forming the enzyme-substrate complex and the reaction speed will not increase, since no free enzymes would remain.
- If the substrate concentration decreases, the number of encounters in enzymes and substrates will be less and the rate of the chemical reaction will decrease.
Activators effect.
- Some ions promote the binding between the enzyme and the substrate.
Effect of inhibitors.
- Inhibitors are substances that decrease the effectiveness of an enzyme. The inhibition can be of two:
  - The irreversible inhibition when the inhibitor is permanently fixed to the active site of the enzyme by altering their structure and thus making it unusable.
  - The reversible inhibition when temporarily prevents normal operation of the enzyme without disabling the active center. There are two ways:
    - The reversible inhibition competitive occurs when the inhibitor is similar to the substrate, so that both can bind to the active center of the enzyme.
    - The reversible inhibition noncompetitive is due to an inhibitor that binds to the enzyme by a different site to which the substrate does, by altering its conformation.
  - A special case of inhibition is uncompetitive inhibition, in which the inhibitor does not bind to the free enzyme, but to the enzyme-substrate complex to prevent product formation.

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Skip navigation Biology 2nd Baccalaureate Biology 2nd Bac. 1. Bioelements and biomolecules. Water and mineral salts 1.1. Chemical bonds in biology 1.1.1. Intramolecular bonds 1.1.1.1. Covalent bond 1.1.1.2. Ionic bond 1.1.2. Intermolecular bonds 1.1.2.1. Van der Waals forces 1.1.2.2. Hydrogen bonds 1.2. The chemical basis of life: inorganic and organic components 1.2.1. Primary bioelements 1.2.2. Secondary bioelements 1.2.3. Trace elements 1.3. The immediate principles or biomolecules 1.3.1. Water 1.3.1.1. Chemical structure of water 1.3.1.2. Properties and functions of water 1.3.2. Mineral salts 1.3.2.1. Functions of salts in solution 1.3.2.2. Colloidal solutions and dispersions 1.3.2.3. Properties of colloidal dispersions 1.3.2.4. Diffusion, osmosis and dialysis 1.3.2.4.1. Diffusion 1.3.2.4.2. Osmosis 1.3.2.4.3. Dialysis 1.4. Bibliography 2. Glucides 2.1. Glucid concept 2.2. Classification of carbohydrates 2.3. Monosaccharides 2.3.1. Trioses 2.3.1.1. Spatial isomerism or stereoisomerism 2.3.2. Tetroses 2.3.3. Pentoses 2.3.3.1. Monosaccharide cyclization 2.3.4. Hexoses 2.4. The N-glucosidic and O-glucosidic bonds 2.4.1. Substances derived from monosaccharides 2.5. Disaccharides 2.6. Polysaccharides 2.6.1. Homopolysaccharides 2.6.1.1. Reserve homopolysaccharides 2.6.1.2. Structural homopolysaccharides 2.6.2. Heteropolysaccharides 2.6.3. Heterosides 2.7. General functions of glucides 2.8. Bibliography 3. Lipids 3.1. Lipid concept 3.2. Classification of lipids 3.2.1. Fatty acids 3.2.1.1. Saturated and unsaturated fatty acids 3.2.1.2. Chemical properties of fatty acids 3.2.1.3. Physical properties of fatty acids 3.2.1.4. Fatty Acid Functions 3.2.2. Saponifiable lipids or with fatty acids 3.2.2.1. Simple lipids 3.2.2.1.1. Acylglycerides 3.2.2.1.2. Cerides 3.2.2.2. Complex lipids 3.2.2.2.1. Phospholipids 3.2.2.2.2. Glycolipids 3.2.3. Unsaponifiable lipids or without fatty acids 3.3. Lipid functions 3.4. Bibliography 4. Proteins 4.1. Introduction to proteins 4.2. Amino acids 4.2.1. Classification of amino acids 4.2.2. Properties of amino acids 4.3. The peptide bond 4.4. Protein 4.4.1. Protein structure 4.4.1.1. Primary structure of proteins 4.4.1.2. Secondary structure of proteins 4.4.1.3. Tertiary structure of proteins 4.4.1.4. Quaternary structure of proteins 4.4.2. Protein properties 4.4.3. Classification of proteins 4.4.3.1. Holoproteins 4.4.3.2. Heteroproteins 4.4.4. Protein functions 4.5. Enzymes 4.5.1. Structure of enzymes 4.5.2. The active center of enzymes 4.5.3. General Mechanism of Enzyme Catalysis 4.5.4. Regulation of enzyme activity 4.5.5. Allosteric enzymes 4.5.6. Nomenclature and classification of enzymes 4.6. The vitamins 4.6.1. Fat-soluble vitamins 4.6.2. Water soluble vitamins 4.7. Bibliography 5. Nucleotides and nucleic acids 5.1. The chemical composition of nucleic acids 5.1.1. Components of nucleic acids 5.1.2. Concept, types and functions of nucleic acids 5.1.3. Nucleosides 5.1.4. Nucleotides 5.1.4.1. Nucleotide functions 5.1.5. Nucleic acids 5.2. Deoxyribonucleic acid (DNA) 5.2.1. DNA structure 5.2.1.1. Primary structure of DNA 5.2.1.2. Secondary structure of DNA 5.2.1.3. Tertiary structure of DNA 5.2.1.3.1. Tertiary structure of DNA in prokaryotes 5.2.1.3.2. Tertiary structure of DNA in eukaryotes 5.2.1.4. Quaternary structure of DNA 5.2.2. DNA types 5.2.3. Genetic material: chromatin and chromosomes 5.2.3.1. Karyotype and karyogram 5.3. Ribonucleic acid (RNA) 5.3.1. RNA types 5.3.1.1. Transfer RNA 5.3.1.2. Messenger RNA 5.3.1.3. Ribosomal RNA 5.3.1.4. Nucleolar RNA 5.3.1.5. Small nuclear RNA 5.3.2. Functions of ribonucleic acids 5.4. Bibliography 6. Cell morphology 6.1. Cell concept 6.1.1. Cell history 6.1.2. Cell theory 6.2. Levels of cellular organization 6.2.1. General characteristics of cells 6.2.2. Prokaryotic cells 6.2.2.1. Prokaryotic cell morphology 6.2.2.2. Structure of prokaryotes 6.2.2.2.1. Bacterial capsule 6.2.2.2.2. Bacterial wall 6.2.2.2.3. Plasma membrane 6.2.2.2.4. Cytoplasm-Ribosomes-Inclusions 6.2.2.2.5. Bacterial DNA 6.2.2.2.6. Bacterial appendages 6.2.2.3. Bacteria Physiology 6.2.3. Eukaryotic cells 6.2.3.1. Animal and plant cell 6.2.3.1.1. Animal eukaryotic cell 6.2.3.1.2. Plant eukaryotic cell 6.2.3.2. Cell Evolution: Endosymbiont Theory 6.3. Size, shape and quantity 6.4. The plasma membrane 6.4.1. Chemical composition of the membrane 6.4.2. The structure of the membrane. The fluid mosaic model 6.4.3. Functions of the plasma membrane 6.4.4. Transport across the membrane 6.4.4.1. Small molecule transport 6.4.4.2. Macromolecule transport 6.4.5. Plasma membrane differentiations 6.5. The cell wall of plant cells 6.5.1. Chemical composition of the cell wall 6.5.2. Cell wall structure 6.5.3. Cell wall differentiations 6.5.4. Cell wall functions 6.6. Extracellular matrix or glucocalyx 6.7. Cytosol or hyaloplasm 6.8. The cytoskeleton 6.8.1. Microfilaments or actin filaments 6.8.2. Intermediate filaments 6.8.3. Microtubules 6.9. Cell membrane and organelle systems 6.9.1. Membrane systems 6.9.1.1. The endoplasmic reticulum 6.9.1.2. Golgi apparatus 6.9.2. Cell organelles 6.9.2.1. Lysosomes 6.9.2.2. Peroxisomes 6.9.2.3. Vacuoles 6.9.2.4. Mitochondria 6.9.2.4.1. Functions of the mitochondria 6.9.2.5. Plastids 6.9.2.5.1. Chloroplasts 6.9.2.6. Ribosomes 6.9.2.7. Centrosome 6.9.2.8. Cilia and flagella 6.10. Cell motility 6.11. The cell nucleus 6.11.1. Characteristics of the cell nucleus 6.11.2. The interphase nucleus 6.11.3. The mitotic nucleus or nucleus in division 6.12. Bibliography 7. Metabolism 7.1. Metabolism 7.1.1. Energetic Aspects of Cellular Chemical Reactions 7.2. Catabolism 7.2.1. Catabolism and obtaining energy 7.2.2. Carbohydrate catabolism 7.2.2.1. Glycolysis 7.2.2.2. Cellular respiration 7.2.2.2.1. Oxidative decarboxylation 7.2.2.2.2. Krebs cycle 7.2.2.2.3. Electron transport chain 7.2.2.2.4. Energy balance of cellular respiration 7.2.2.3. Fermentations 7.2.2.3.1. Alcoholic or ethyl fermentation 7.2.2.3.2. Lactic fermentation 7.2.2.3.3. Other types of fermentations 7.3. Anabolism 7.3.1. Autotrophic anabolism 7.3.2. Photosynthesis 7.3.2.1. Photochemical or light phase 7.3.2.1.1. Photosystems 7.3.2.1.2. Photophosphorylation 7.3.2.1.2.1. Non cyclic photophosphorylation 7.3.2.1.2.2. Cyclic photophosphorylation 7.3.2.2. Biosynthetic or dark phase 7.3.2.3. Factors influencing photosynthesis 7.3.2.4. Products of photosynthesis 7.3.3. Chemosynthesis 7.4. Bibliography 8. Cell reproduction 8.1. The cell cycle 8.1.1. Interphase 8.1.2. Cellular division 8.2. Cellular division 8.2.1. Mitosis 8.2.1.1. Prophase 8.2.1.2. Metaphase 8.2.1.3. Anaphase 8.2.1.4. Telophase 8.2.1.5. Cytokinesis 8.2.1.6. More on mitosis 8.2.2. Meiosis 8.2.2.1. Meiosis I 8.2.2.2. Meiosis II 8.2.3. Meiosis and sexual reproduction 8.2.4. Meiosis and life cycle 8.2.5. Biological importance of meiosis 8.3. Differences and similarities between mitosis and meiosis 8.4. Bibliography 9. Classical genetics 9.1. Genetics basics 9.2. Mendelian genetics 9.2.1. The method 9.2.2. Mendel's Laws 9.2.2.1. Mendel's first law or principle of uniformity in the first generation 9.2.2.2. Mendel's second law or principle of segregation 9.2.2.2.1. Backcross and test crossover 9.2.2.3. Mendel's third law or principle of independent combination 9.3. Gene interaction 9.3.1. Gene interaction between allelic genes 9.3.2. Gene interaction between non-allelic genes that influence for the same trait 9.4. Chromosomal theory of heredity 9.5. Ligation and recombination 9.6. Complex mendelism 9.6.1. Multiple allelism 9.6.1.1. Lethal genes 9.6.2. Pleiotropy 9.6.3. Expressiveness and genetic penetrance 9.7. Sex-linked inheritance 9.7.1. Y-linked inheritance 9.7.2. X-linked inheritance 9.8. Heredity influenced by sex 9.9. Bibliography 10. Molecular genetics 10.1. DNA as hereditary material 10.2. DNA replication 10.2.1. The need for DNA replication 10.2.2. First hypotheses about DNA duplication 10.2.3. Meselson and Stahl experiment 10.2.4. The sense of growth of the new strands 10.2.5. Mechanism of DNA replication 10.2.5.1. Replication in prokaryotes 10.2.5.2. Replication in eukaryotes 10.2.6. Error correction 10.2.7. Enzymes involved in replication 10.3. Gene concept 10.4. "One gene-one enzyme" theory 10.5. Transcription 10.5.1. Mechanism of transcription 10.5.1.1. Transcription in prokaryotes 10.5.1.2. Eukaryotic transcription 10.6. Translation or protein biosynthesis 10.6.1. The genetic code 10.6.2. Mechanism of translation of RNA to proteins 10.6.2.1. Translation in eukaryotes 10.7. Regulation of gene expression 10.8. Bibliography 11. Genetics and evolution 11.1. Mutations 11.2. Types of mutations 11.2.1. Gene or point mutation 11.2.2. Chromosomal or structural mutation 11.2.3. Mutation at the genomic level 11.3. Causes of mutations 11.4. Evolutionary implications of mutations 11.5. Metabolic implications of mutations 11.6. Bibliography 12. Microbiology and biotechnology 12.1. Microbiology 12.2. Viruses 12.2.1. Viral morphology 12.2.2. Viral physiology 12.2.2.1. Lytic cycle 12.2.2.2. Lysogenic cycle 12.2.2.3. Cycles of viruses of special interest 12.2.2.3.1. Flu virus life cycle 12.2.2.3.2. Life cycle of the AIDS virus 12.3. Other acellular forms 12.3.1. Viroids 12.3.2. Prions 12.4. Biotechnology 12.5. Bibliography 13. Immunology 13.1. Infection concept 13.2. Defense mechanisms against infections 13.2.1. Nonspecific mechanisms 13.2.1.1. Primary barriers: external defenses 13.2.1.2. Secondary barriers: internal defenses 13.2.2. Specific mechanisms 13.3. Immunity and immune system 13.3.1. Components of the immune system 13.3.2. Concept and nature of antigens 13.4. The immune response 13.4.1. Humoral immune response: the antibodies 13.4.1.1. Antibody-producing cells: B lymphocytes 13.4.1.2. Antibodies 13.4.1.2.1. Types of antibodies 13.4.1.2.2. Antigen-antibody reaction 13.4.1.3. Immune memory: primary and secondary responses 13.4.2. Cellular immune response: T lymphocytes 13.5. Types of immunity 13.5.1. Natural immunity 13.5.2. Artificial immunity 13.6. Immune system disorders 13.6.1. Autoimmunity 13.6.2. Hypersensitivity 13.6.3. Immunodeficiency 13.6.4. Transplants and the phenomenon of rejections 13.7. Bibliography « Previous \| Next » 4.5.4. Regulation of enzyme activity Regulation of enzyme activity The rate of enzymatic reactions depends on a number of factors, including the following: Influence of temperature. Influence of pH. Influence of the substrate concentration. Activators effect. Effect of inhibitors. Influence of temperature If we supply energy in the form of heat to an enzymatic reaction, when it is captured by the molecules it is transformed into kinetic energy. In this way, the movement of the molecules and the number of intermolecular encounters increases. Thus, increasing the temperature increases the speed of chemical reactions. If the temperature is too high, the enzyme loses its tertiary structure, becomes denatured and ceases to be functional. There is an optimal temperature for which the enzymatic activity is maximum. If you decrease the temperature, the activity also decreases, but the enzyme is not destroyed, and the process is reversible. Influence of pH All enzymes have an *optimal pH* at which they are most effective, although they can function between two pH limit values. If the pH is outside these limits, the enzyme denatures and stops working. Influence of substrate concentration If you increase the substrate concentration, keeping the enzyme concentration constant , the rate of the reaction increases. As there are more substrate molecules, the enzyme-substrate encounter is more likely to occur. This increase in speed has a limit, since if the substrate concentration is excessive, all enzymes will be in the ES complex form, they will be saturated, and the reaction speed will not increase. If the substrate concentration is decreased, the rate of the chemical reaction will decrease. Activators effect There are some ions that favor the binding between the enzyme and the substrate. For example, the enzyme phosphorylase is activated by the presence of magnesium ions Mg²⁺, forming ATP from ADP and a phosphate group (H₃PO₄). Effect of inhibitors Inhibitors are substances that decrease the activity and effectiveness of an enzyme or completely prevent its action. Inhibition can be of two types: irreversible and reversible. The irreversible inhibition or poisoning of the enzyme occurs when the inhibitor is permanently fixed to the active site of the enzyme by altering their structure and thus making it unusable. The reversible inhibition occurs when temporarily prevents normal operation of the enzyme without disabling the active center. There are two ways: competitive and non- competitive. The reversible inhibition competitive occurs when the inhibitor is similar to the substrate, so that both can bind to the active center of the enzyme. If the substrate is attached to the enzyme, the products are formed. If the inhibitor is fixed, the enzyme cannot act until it is released from the inhibitor. The reversible inhibition noncompetitive is due to an inhibitor that binds to the enzyme by a different site to which the substrate does, by altering its conformation. It can also act on the enzyme-substrate complex, making it fixed. A special case of inhibition is uncompetitive inhibition, in which the inhibitor does not bind to the free enzyme, but to the enzyme-substrate complex to prevent product formation. Fundamental insights on the regulation of enzyme activity The speed of enzymatic reactions depends on several factors: Influence of temperature. As the temperature increases to an optimum temperature, the molecules move faster and the number of encounters between molecules is greater, thus increasing the speed of the reaction. If the temperature continues to increase, the formation of the enzyme-substrate complex becomes more difficult and the reaction speed decreases, in addition to the denaturation of the enzyme and the loss of its functionality, since it loses its secondary, tertiary structures (mainly) and quaternary. The denaturation is usually irrerversible, although again lower the temperature, the enzyme does not recover its native three - dimensional structure. Sometimes, if it has been subjected to denaturing factors and low intensity for a short time, denaturation can be reversible. Influence of pH. Each enzyme has its maximum activity (maximum reaction rate) at a certain pH called the optimum pH. Outside this pH, the structure of the enzyme is altered and its catalytic capacity is less effective. Influence of the substrate concentration. As the concentration of substrate increases, if the concentration of the enzyme does not vary, it is more likely that encounters between enzymes and substrates will occur, thus the reaction rate increases. If the substrate concentration is excessive, all the enzymes will be saturated forming the enzyme-substrate complex and the reaction speed will not increase, since no free enzymes would remain. If the substrate concentration decreases, the number of encounters in enzymes and substrates will be less and the rate of the chemical reaction will decrease. Activators effect. Some ions promote the binding between the enzyme and the substrate. Effect of inhibitors. Inhibitors are substances that decrease the effectiveness of an enzyme. The inhibition can be of two: The irreversible inhibition when the inhibitor is permanently fixed to the active site of the enzyme by altering their structure and thus making it unusable. The reversible inhibition when temporarily prevents normal operation of the enzyme without disabling the active center. There are two ways: The reversible inhibition competitive occurs when the inhibitor is similar to the substrate, so that both can bind to the active center of the enzyme. The reversible inhibition noncompetitive is due to an inhibitor that binds to the enzyme by a different site to which the substrate does, by altering its conformation. A special case of inhibition is uncompetitive inhibition, in which the inhibitor does not bind to the free enzyme, but to the enzyme-substrate complex to prevent product formation. Licensed under the Creative Commons Attribution Share Alike License 4.0 « Previous \| Next » These pages are semi-automatically translated from the web Biology 2nd Baccalaureate. Biología de 2º de Bachillerato (biologia-geologia.com). You can make any suggestion, question, comment, ..., in our forum 2º Bachillerato Biología - Foro de biologia-geologia.com
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