Questions and Answers
What is the function of an enzyme?
What is catalysis?
The acceleration of a reaction rate by a molecule that is unchanged by participating in the reaction.
What does specificity refer to in enzymes?
Enzymes exhibit preference for certain types of substrates based on their physical and chemical structure.
What are coenzymes?
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What are prosthetic groups?
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List factors that can influence enzyme activity: ____, ____, ____, and ___.
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Match the following classes of enzymes with their reactions:
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Which coenzyme is commonly required by Oxidoreductases?
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What is the significance of different enzymes localized in different parts of the body?
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What type of enzymes are localized in lysosomes?
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What is a proenzyme?
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What are isozymes?
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How can isozyme analysis be useful in diagnosing disease?
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Following an acute myocardial infarction, one would expect changes in plasma lactate dehydrogenase (LDH) _____.
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Study Notes
Enzyme Overview
- Enzymes act as catalysts, significantly increasing the rate of biochemical reactions without being consumed.
- Catalysis refers to the acceleration of a reaction rate by a molecule that remains unchanged after the reaction.
Key Enzyme Characteristics
- Specificity: Enzymes exhibit a preference for certain substrates based on their physical and chemical structure.
- Coenzymes and cofactors are auxiliary substances that may be required for enzymatic activity, with some binding reversibly while others bind tightly.
- Prosthetic groups are tightly-bound coenzymes that do not dissociate from enzymes, though altered during reactions.
Factors Influencing Enzyme Activity
- Substrate and enzyme concentrations affect reaction direction; increased reactants push the reaction right while increased products push it left.
- Temperature can enhance enzyme activity, but excessively high temperatures may denature proteins.
- pH levels influence enzyme activity based on the ionization of catalytic groups; extremes in pH can lead to denaturation.
- Activators and inhibitors can modify enzyme structure and function.
Major Classes of Enzymes
- Oxidoreductases: Catalyze oxidation-reduction reactions, often requiring coenzymes (e.g., dehydrogenases, oxidases).
- Transferases: Facilitate group transfers (e.g., kinases, transaminases).
- Hydrolases: Catalyze bond cleavage with water addition (e.g., peptidases, amylases).
- Lyases: Induce bond cleavage without water (e.g., decarboxylases, synthases).
- Isomerases: Assist in rearranging isomers (e.g., mutases, racemases).
- Ligases: Form bonds using energy from high-energy compounds like ATP (e.g., synthetases, carboxylases).
Coenzymes and Their Associated Enzymes
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For Oxidoreductases:
- Cu2+/Cu+ in Cytochrome C oxidase
- FAD/FADH2 in Succinate Dehydrogenase
- NAD+/NADH in Lactate Dehydrogenase and Alcohol Dehydrogenase
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For Transferases:
- ATP/ADP in various kinases
- Pyridoxal phosphate in aminotransferases
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For Ligases:
- ATP and Biotin in Pyruvate Carboxylase
Enzyme Localization and Significance
- Enzymes are precisely located in organs, tissues, and cells based on their specific functions; for example, hydrolases are found in lysosomes, while DNA polymerase is localized in nuclei.
- Tissue-specific enzymes reflect the different metabolic needs of organs (e.g., liver vs. adipose tissue).
Proenzymes and Isozymes
- Proenzymes (zymogens) contain activation sites which, upon cleavage, produce active enzymes with variations in amino acid sequences.
- Isozymes are enzymes with different amino acid sequences but catalyze the same reaction, reflecting genetic differences in polypeptides (e.g., multiple forms of lactate dehydrogenase).
Clinical Relevance of Isozyme Analysis
- Elevated levels of lactate dehydrogenase (LDH) in plasma can indicate tissue damage, making isozyme analysis a valuable tool in diagnosing conditions like myocardial infarction.
- Changes in LDH isozymes can reflect specific health issues (e.g., increased levels post-acute myocardial infarction or acute hepatitis).
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Description
Test your knowledge of enzyme terminology with these flashcards. Each card features a key term related to enzymatic reactions, along with its definition. Perfect for students studying biochemistry or related fields!
