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Questions and Answers
Enzymes are proteins that act as biological catalysts by __________ chemical reactions.
What are the molecules upon which enzymes may act called?
In enzyme specificity, a small change in the shape of the substrate can cause a major change in the behavior of the __________.
What does allostery refer to in terms of enzyme function?
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What is the term for enzymes that have an additional allosteric site besides the active site?
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What is the special pocket in enzymes that has a high specificity?
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Which class of enzymes catalyzes the synthesis of DNA and RNA?
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What type of reaction do ATPases catalyze?
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What is the term for the metabolically active form of vitamins often required by enzymes?
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What role does the active site play in enzyme catalysis?
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Which point in a reaction pathway is considered the highest energy point?
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What suffix is most commonly used in enzyme nomenclature?
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What is the primary function of apoenzyme in enzyme catalysis?
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In enzyme nomenclature, what type of name is used when an enzyme must be identified without ambiguity?
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Which class of enzymes catalyzes reactions involving the oxidation of one molecule and the reduction of another?
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What type of enzyme catalyzes the rearrangement of bonds within a single molecule?
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Which enzyme removes phosphates from molecules?
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What is the difference between an enzyme with the suffix -ase and one with the suffix -synthase?
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In enzyme nomenclature, what do dehydrogenases catalyze?
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Which term refers to the protein part of an enzyme molecule without its cofactor?
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What is the primary function of an enzyme cofactor?
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Enzymes speed up biochemical reactions by:
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Which property of enzymes allows them to be highly specific in their substrate recognition?
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In enzyme nomenclature, what do the letters 'ES' represent in the reaction E + S ES?
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What type of regulation occurs when a molecule binds to an enzyme at a site other than the active site, altering its activity?
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Which of the following best describes the role of enzymes in life processes?
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What is the function of cofactors in enzyme catalysis?
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Enzymes that are found in specific organelles in the cell contribute to what property that helps avoid competition for substrates or create more favorable conditions?
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What is the term used for the complete, catalytically active form of an enzyme with its bound cofactor?
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Which term refers to the molecules that are acted upon by enzymes during catalytic reactions?
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Study Notes
Enzymes: General Concepts
- Enzymes are proteins that act as biological catalysts, accelerating chemical reactions in biological systems.
- They play a fundamental role in metabolic events, signal transduction, and cell regulation.
- Enzymes have a high degree of specificity for their substrates and accelerate chemical reactions tremendously without being changed or used up during the process.
Enzyme Binding and Specificity
- The binding of enzymes to substrates is very specific, with small changes in the shape of the ligand/substrate causing major changes in protein behavior.
- Complementary shape recognition plays a major role in information transfer.
- Allostery is the ability of a protein to change shape, resulting in a change in binding affinity at a different binding site.
Classes of Enzymes
- Polymerases: catalyze polymerization reactions such as DNA and RNA synthesis.
- Proteases: break down proteins by hydrolyzing bonds between amino acids.
- Kinases: catalyze the addition of phosphate groups to molecules.
- ATPases: hydrolyze ATP.
- Synthases: synthesize molecules in anabolic reactions by condensing two smaller molecules together without using ATP.
- Phosphatase: catalyze the hydrolytic removal of a phosphate group from a molecule.
Properties and Characteristics of Enzymes
- Active sites: enzymes contain a special pocket called the active site, which has high specificity and contains amino acid side chains that participate in substrate binding and catalysis.
- Enzymes are reusable, sensitive to pH changes, and denatured by high heat.
- They can be inhibited by poison.
- Catalytic efficiency: reactions catalyzed by enzymes are 10^3-10^8 times faster than uncatalyzed reactions.
- Specificity: enzymes interact with one or very few substrates and catalyze only one type of chemical reaction.
Location and Compartmentalization of Enzymes
- Many enzymes are located in specific organelles in the cell and in specific cells, enabling compartmentalization and isolation of reactions.
Enzymatic Diagnosis
- Testing for specific enzymes provides information about the organs and tissues in the body as well as the metabolic state of the animal.
- Examples of enzymes used in diagnosis include ALT, ALP, Amylase, Lipase, CK, and AST.
The Transition State
- The active site acts as a molecular template that binds the substrate and initiates its conversion to the transition state.
- The transition state is the form the substrate must take before it becomes a product.
- Enzymes stabilize the transition state, increasing the concentration of the reactive intermediate that can be converted to product, accelerating the reaction.
Nomenclature of Enzymes
- Recommended names: short names with the suffix '-ase' attached to the substrate of the reaction.
- Systematic names: more complete, complex, and used when an enzyme must be identified without ambiguity.
- Examples of enzymes with trivial names include LDH (lactate dehydrogenase) and ATPase.
Major Classes of Enzymes
- Oxidoreductases: catalyze reactions in which one molecule is oxidized while the other is reduced.
- Transferases: transfer carbon, nitrogen, or phosphate groups.
- Hydrolases: catalyze a hydrolytic cleavage reaction.
- Lyases: catalyze the cleavage of C-C, C-S, and C-N bonds.
- Isomerases: catalyze the rearrangement of bonds within a single molecule.
- Ligases: join two molecules in an energy-dependent process.
Industrial Applications of Enzymes
- Biofuel production
- Agricultural industry (animal feed additives, fertilizers…)
- Fermentations (transformation of raw materials)
- Biotransformations (transformation of defined precursors to a desired target product)
- Pharmaceutical industry (synthesis & modification of antibiotics & medicines)
- Diagnosis of disease (increased or decreased concentrations of enzyme activity)
- Treatment of disease (e.g., enzyme replacement therapy)
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Description
Test your knowledge on enzyme nomenclature with a focus on the suffix -ase and systematic names. Learn about the major classes of enzymes and how they catalyze reactions. Part 1 of the quiz series.
