9.8.5 - Classification and Nomenclature of Enzymes
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Introduction to Enzymes
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Today we are going to learn about enzymes and the critical roles they play in biochemical reactions. Can anyone tell me what enzymes are?
Are they proteins that speed up chemical reactions?
Exactly! Enzymes are proteins that act as catalysts. They can speed up reactions by lowering the activation energy. Now, enzymes are classified into several categories based on the type of reactions they catalyze. Let’s explore these classifications.
How many classes are there?
There are six main classes of enzymes. Let's talk about them one by one.
Oxidoreductases and Transferases
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The first class is Oxidoreductases, which facilitate oxidation-reduction reactions. Can someone give me an example of such a reaction?
Isn't that like when iron rusts, involving the transfer of electrons?
Great example! Now, what about Transferases? What do they do?
They transfer groups like methyl or phosphate between molecules, right?
Exactly! Now remember this acronym to help you memorize: O for Oxidation and T for Transfer. Let’s keep going!
Hydrolases and Lyases
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Next are Hydrolases. Who can tell me what these enzymes do?
They break down substances by adding water!
Exactly! A common reaction is the breakdown of sucrose into glucose and fructose. And what about Lyases?
They remove groups from molecules to form double bonds!
Correct! Let's remember 'H for Hydrolysis' and 'L for Lyases' with the mnemonic: 'Help Losing water' for Hydrolases.
Isomerases and Ligases
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The fifth class is Isomerases. What do they accomplish?
They help convert one isomer into another!
Very good! Isomerases help with rearranging molecules. Finally, Ligases join two compounds together—can anyone give an example?
Like how DNA ligase links DNA fragments!
Exactly! To summarize: we have O for Oxidoreductases, T for Transferases, H for Hydrolases, L for Lyases, I for Isomerases, and L for Ligases.
Importance of Enzyme Classification
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Why do you think classifying enzymes is important?
So we can easily identify and study their functions?
Correct! Each enzyme class can be assigned a four-digit numerical code, allowing for easier communication in biochemical research. Remembering this is critical for understanding metabolic pathways.
Is this classification used in research?
Absolutely! It is essential for research and applications in biotechnology. The better we understand enzymes, the more we can harness their powers.
Introduction & Overview
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Quick Overview
Standard
Enzymes play a crucial role in biological reactions and are categorized into six classes based on the nature of the reactions they catalyze. Each class includes subclasses and is identified by a systematic four-digit number. This classification helps in understanding their diverse functions in metabolic pathways.
Detailed
Classification and Nomenclature of Enzymes
Enzymes are biological catalysts that facilitate biochemical reactions in living organisms. A vast number of enzymes have been identified, and they are systematically classified into six main categories based on the type of reaction they catalyze. The classes are defined as follows:
- Oxidoreductases/Dehydrogenases: These enzymes catalyze oxidation-reduction reactions involving the transfer of electrons between substrates. For instance, if a substrate 'S' is reduced, another substrate 'S'' becomes oxidized.
- Transferases: These enzymes are responsible for transferring functional groups (G) from one substrate to another, altering their composition. For example, the reaction could involve two substrates where a group is removed from one and added to another.
- Hydrolases: Enzymes in this class catalyze hydrolysis reactions, breaking down various bond types including ester, ether, peptide, and glycosidic bonds by introducing water.
- Lyases: These enzymes remove groups from substrates through mechanisms other than hydrolysis, resulting in the formation of double bonds.
- Isomerases: This class includes enzymes that facilitate the interconversion of isomers, helping in the rearrangement of the molecular structure of substrates.
- Ligases: Enzymes categorized as ligases catalyze the joining of two compounds (like C-O, C-N bonds), often involving coupling reactions that require energy.
Each enzyme class is assigned a four-digit number for precise identification, enabling researchers to catalog and study specific enzymes efficiently. This classification system not only aids in understanding the diverse functions of enzymes in different metabolic processes but also establishes a framework for enzyme research and application in biotechnology.
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Enzyme Classification Overview
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Chapter Content
Thousands of enzymes have been discovered, isolated and studied. Most of these enzymes have been classified into different groups based on the type of reactions they catalyse. Enzymes are divided into 6 classes each with 4-13 subclasses and named accordingly by a four-digit number.
Detailed Explanation
Enzymes are biological catalysts that increase the rate of chemical reactions in living organisms. They are categorized into six main classes based on the type of reaction each enzyme facilitates. Each of these classes can have further subclasses, making it easy for scientists to identify and study specific enzymes. The classification system helps biologists and chemists understand the functions of enzymes and their roles in metabolic processes.
Examples & Analogies
Think of enzymes like different types of workers in a factory. Each worker has a specific job, and they specialize in that task. Just like how some workers might build things (transferases) while others clean up scraps (hydrolases), enzymes work on different reactions in our body. This classification helps researchers quickly find the right 'worker' for the job based on the type of reaction they require.
Oxidoreductases
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Chapter Content
Oxidoreductases/dehydrogenases: Enzymes which catalyse oxidoreduction between two substrates S and S’ e.g., S reduced + S’ oxidised → S oxidised + S’ reduced.
Detailed Explanation
Oxidoreductases are a class of enzymes that facilitate oxidation-reduction reactions, where one molecule is oxidized (loses electrons) and another is reduced (gains electrons). This is important in biological processes like cellular respiration, where energy is extracted from food.
Examples & Analogies
Imagine a battery: when you charge it, you're essentially reducing it, and when it's used to power a device, it gets oxidized. Similarly, oxidoreductases help rearrange electrons in molecules for energy exchange during metabolic processes.
Transferases
Chapter 3 of 7
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Chapter Content
Transferases: Enzymes catalysing a transfer of a group, G (other than hydrogen) between a pair of substrate S and S’ e.g., S - G + S’ → S + S’ - G.
Detailed Explanation
Transferases are enzymes that move functional groups from one molecule (substrate) to another. This process is vital for synthesizing larger biomolecules, such as when building amino acids or nucleotides, where various functional groups need to be exchanged.
Examples & Analogies
Think of transferases like a schoolyard game of tag, where a player (the functional group) is transferred from one child (substrate) to another. Each time someone gets tagged, they have a new role, just like molecules are transformed in biochemical reactions.
Hydrolases
Chapter 4 of 7
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Chapter Content
Hydrolases: Enzymes catalysing hydrolysis of ester, ether, peptide, glycosidic, C-C, C-halide or P-N bonds.
Detailed Explanation
Hydrolases are enzymes that catalyze hydrolysis reactions, where a water molecule is used to break chemical bonds in larger molecules. This is crucial for digestion, breaking down proteins into amino acids and carbohydrates into sugars.
Examples & Analogies
Imagine hydrolases as a pair of scissors cutting a long piece of ribbon (the large molecule) into smaller pieces (the smaller molecules). Just as scissors help segment the ribbon into manageable pieces, hydrolases help our bodies digest food.
Lyases
Chapter 5 of 7
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Lyases: Enzymes that catalyse removal of groups from substrates by mechanisms other than hydrolysis leaving double bonds.
Detailed Explanation
Lyases are enzymes that remove groups from substrates without the addition of water (unlike hydrolases). This removal often leads to the formation of double bonds in the substrate, playing important roles in metabolic pathways.
Examples & Analogies
Think of lyases like sculptors chiseling away at a block of marble. Instead of adding material (like water), they remove pieces to reveal a new shape (the double bond) from the substrate.
Isomerases
Chapter 6 of 7
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Chapter Content
Isomerases: Includes all enzymes catalysing inter-conversion of optical, geometric or positional isomers.
Detailed Explanation
Isomerases are enzymes that facilitate the interconversion of isomers, which are compounds with the same molecular formula but different arrangements or structures. This is important in processes like the conversion of glucose into fructose.
Examples & Analogies
Consider isomerases like a chef rearranging ingredients in a dish. Even if the same basic components are used, changing their arrangement can yield a different flavor (isomer).
Ligases
Chapter 7 of 7
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Chapter Content
Ligases: Enzymes catalysing the linking together of 2 compounds, e.g., enzymes which catalyse joining of C-O, C-S, C-N, P-O etc. bonds.
Detailed Explanation
Ligases are enzymes that catalyze the joining of two molecules, typically accompanied by the expenditure of ATP. These enzymes are vital for processes that involve the synthesis of larger biomolecules, such as DNA replication where nucleotides are linked.
Examples & Analogies
Think of ligases as construction workers connecting two pieces of wood together with nails. Just as nails bind the wood pieces firmly, ligases help link smaller molecules into a larger structure.
Key Concepts
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Enzymes are classified into six main classes based on the reactions they catalyze.
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Each enzyme class has a systematic naming convention with a four-digit numerical code.
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Oxidoreductases involve oxidation-reduction processes.
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Transferases transfer functional groups between molecules.
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Hydrolases catalyze hydrolysis reactions, while Lyases break bonds to form double bonds.
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Isomerases facilitate structural rearrangements of molecules.
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Ligases link together two compounds, often requiring energy input.
Examples & Applications
Oxidoreductases include lactate dehydrogenase, which interconverts lactate and pyruvate.
Transferases include amino transferases that transfer amino groups between amino acids.
Hydrolases include digestive enzymes like amylase, which breaks down starch.
Lyases include decarboxylases, which remove carboxyl groups from substrates.
Isomerases include glucose-6-phosphate isomerase that converts glucose-6-phosphate to fructose-6-phosphate.
Ligases include DNA ligase, which joins DNA fragments during replication.
Memory Aids
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Rhymes
Oxidoreductases change with gains and losses, Transferases switch groups across all processes.
Stories
Imagine enzymes at a party. Oxidoreductases dance to the rhythm of electrons, while Transferases mingle and share their accessories!
Memory Tools
Remember ‘OHTLLI’ for the enzyme classes: Oxidoreductases, Hydrolases, Transferases, Lyases, Ligases, and Isomerases.
Acronyms
For enzyme functions
OHTLLI represents Oxidation
Hydrolysis
Transfer
Lyase action
Joining
and Isomerizing.
Flash Cards
Glossary
- Enzyme
A protein that catalyzes biochemical reactions by lowering the activation energy.
- Oxidoreductases
Enzymes that catalyze oxidation-reduction reactions.
- Transferases
Enzymes that transfer functional groups between substrates.
- Hydrolases
Enzymes that catalyze hydrolysis reactions, breaking down compounds by adding water.
- Lyases
Enzymes that remove groups from substrates without hydrolysis, forming double bonds.
- Isomerases
Enzymes that facilitate the interconversion of isomers.
- Ligases
Enzymes that catalyze the joining of two compounds.
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