Ethylene glycol (HO—CH₂—CH₂—OH) is a major component of antifreeze. If ingested, it is first converted to HOOC—CHO (oxoethanoic acid) and then to HOOC—COOH (oxalic acid), which is toxic. (16.4, 16.5).


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a. What class of enzyme catalyzes the reactions described?

Verified step by step guidance

1. Identify the type of chemical reaction occurring in the conversion of ethylene glycol to oxoethanoic acid and then to oxalic acid.
2. Recognize that the conversion involves the oxidation of alcohol groups to carboxylic acid groups.
3. Recall that enzymes that catalyze oxidation-reduction reactions are known as oxidoreductases.
4. Consider the specific type of oxidoreductase that acts on the CH-OH group of donors, which are typically dehydrogenases.
5. Conclude that the class of enzyme catalyzing these reactions is likely an oxidoreductase, specifically a dehydrogenase.

Key Concepts

Enzyme Classification

Enzymes are biological catalysts that speed up chemical reactions in the body. They are classified into six main categories based on the type of reaction they catalyze: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Understanding this classification is essential for identifying the specific type of enzyme involved in the conversion of ethylene glycol to its toxic metabolites.

Oxidation-Reduction Reactions

Oxidation-reduction (redox) reactions involve the transfer of electrons between molecules, leading to changes in their oxidation states. In the metabolism of ethylene glycol, the conversion to oxoethanoic acid and subsequently to oxalic acid involves redox processes, typically catalyzed by oxidoreductases. Recognizing these reactions is crucial for understanding the enzymatic pathways involved in the toxicity of ethylene glycol.

Toxic Metabolites

Toxic metabolites are harmful byproducts formed during the metabolism of substances in the body. In the case of ethylene glycol, its metabolism leads to the formation of oxalic acid, which can cause metabolic acidosis and kidney damage. Understanding the nature and effects of these toxic metabolites is vital for assessing the risks associated with ethylene glycol ingestion and the role of enzymes in their production.