Which enzyme class splits a chemical bond in the absence of water?
Multiple Choice
Ligase
Oxidoreductase
Lyase
Hydrolase Dehydrogenase
The correct answer and explanation is:
The correct answer is Lyase.
Lyases are enzymes that break chemical bonds by mechanisms other than hydrolysis or oxidation. This means they can split bonds without the involvement of water, which distinguishes them from other enzymes that require water molecules to facilitate the cleavage. Lyases typically catalyze the removal of a group from a substrate without the need for water and often form a new double bond or ring structure as a result.
For example, in the case of decarboxylases, a type of lyase, the enzyme removes a carboxyl group (CO₂) from a substrate without requiring water. This is different from hydrolases, which do need water to break bonds like ester or peptide bonds. Lyases can also form new bonds, such as in aldolases, where they catalyze the breaking of bonds to form new carbon-carbon bonds.
Lyases play a significant role in various biochemical pathways, including metabolic processes like glycolysis and the citric acid cycle. In glycolysis, enzymes like pyruvate decarboxylase, which is a lyase, facilitate the conversion of pyruvate into acetaldehyde and carbon dioxide. This reaction is important for processes like fermentation, especially in anaerobic conditions where oxygen is not available.
In summary, lyases are key enzymes in metabolic reactions where breaking bonds or forming new ones is necessary without the direct involvement of water molecules. This is why they stand out from other enzyme classes such as hydrolases, which require water, or ligases, which typically form bonds rather than breaking them.