Classification and Nomenclature of Enzymes with Examples | 6 Classes of Enzymes with Examples

Summary

This video provides a clear overview of the six major enzyme classes based on their functions: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Each class is explained with relevant examples from biological pathways such as glycolysis and the Krebs cycle. The video also touches on the evolution of enzyme nomenclature and the importance of understanding these classes in biochemical reactions. The explanations are concise, with examples like succinate dehydrogenase, hexokinase, proteases, aldolase, and glutamate-cysteine ligase, helping viewers grasp the essential roles of enzymes in cellular processes.

Takeaways

• 😀 The International Union of Biochemistry and Molecular Biology proposed a classification system for enzyme-catalyzed reactions, organizing them into six classes.
• 😀 The first enzyme class is Oxidoreductases, which catalyze oxidation-reduction reactions. Examples include oxidase and dehydrogenase enzymes.
• 😀 Oxidoreductases often involve the transfer of hydrogen, as seen in the example of succinate dehydrogenase in the Krebs cycle, where succinate is oxidized to fumarate.
• 😀 Transferases are enzymes that transfer functional groups between molecules. Hexokinase in glycolysis is an example where a phosphate group is transferred from ATP to glucose.
• 😀 Hydrolases catalyze hydrolytic reactions, such as proteases that break down proteins into peptides and free amino acids.
• 😀 Lyases are enzymes that split molecules without using hydrolysis or oxidation, often forming double bonds or rings. An example is aldolase in glycolysis.
• 😀 Isomerases catalyze the rearrangement of atoms within a molecule, as seen in the conversion of glucose-6-phosphate to fructose-6-phosphate during glycolysis.
• 😀 Ligases (formerly known as synthetases) catalyze the joining of two molecules, typically using energy from ATP hydrolysis, such as in the joining of tRNA and its corresponding amino acid.
• 😀 The enzyme glutamate cysteine ligase plays a role in the synthesis of glutathione, an important antioxidant, by joining cysteine and glutamate.
• 😀 The video emphasizes that the classification system is crucial for understanding enzyme functions, and it applies to pathways like glycolysis and the Krebs cycle, offering examples from these pathways.

Q & A

What are the six classes of enzymes proposed by the International Union of Biochemistry and Molecular Biology?

The six classes of enzymes are: 1) Oxidoreductases, 2) Transferases, 3) Hydrolases, 4) Lyases, 5) Isomerases, and 6) Ligases.

What is the main function of oxidoreductases?

Oxidoreductases are enzymes involved in oxidation-reduction reactions, where they catalyze the transfer of electrons or hydrogen atoms between molecules. An example is succinate dehydrogenase in the Krebs cycle.

Can you provide an example of an oxidoreductase enzyme?

An example of an oxidoreductase enzyme is succinate dehydrogenase, which catalyzes the oxidation of succinate to form fumarate in the Krebs cycle.

What are transferases and how do they function?

Transferases are enzymes that catalyze the transfer of functional groups from one molecule to another. For example, hexokinase transfers a phosphate group from ATP to glucose, converting it into glucose-6-phosphate.

What is the role of hexokinase in glycolysis?

Hexokinase catalyzes the first step of glycolysis, where it transfers a phosphate group from ATP to glucose, forming glucose-6-phosphate.

What do hydrolases do, and can you provide an example?

Hydrolases are enzymes that catalyze the hydrolytic cleavage of bonds, breaking larger molecules into smaller ones. An example is protease, which breaks down proteins into amino acids.

What is the difference between hydrolysis and oxidation in enzymatic reactions?

Hydrolysis involves the breaking of bonds by adding water (e.g., hydrolyzing peptide bonds), whereas oxidation involves the loss of electrons or hydrogen atoms, often coupled with reduction reactions.

How do lyases function, and can you give an example?

Lyases are enzymes that catalyze the breaking of bonds without hydrolysis or oxidation, often forming double bonds or rings. For example, aldolase in glycolysis splits fructose 1,6-bisphosphate into two 3-carbon molecules.

What is the significance of isomerases in biochemical reactions?

Isomerases are enzymes that rearrange the atoms within a molecule to form isomers. An example is glucose-6-phosphate isomerase, which converts glucose-6-phosphate into fructose-6-phosphate.

What is the role of ligases in molecular biology?

Ligases are enzymes that join two molecules together, typically forming new bonds using the energy from ATP or other triphosphates. An example is DNA ligase, which joins DNA fragments in recombinant DNA technology.