Which enzyme catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate in the TCA cycle?

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Multiple Choice

Which enzyme catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate in the TCA cycle?

Explanation:
In the TCA cycle, the step that converts isocitrate into α-ketoglutarate involves removing a carboxyl group while also oxidizing the molecule, and this is carried out by isocitrate dehydrogenase. As it oxidizes isocitrate, the enzyme transfers electrons to NAD+, forming NADH, and releases carbon dioxide. This combination of oxidation and decarboxylation is what defines this particular reaction. Aconitase, instead, just rearranges citrate to isocitrate via an intermediate called cis-aconitate, without removing CO2. Malate dehydrogenase oxidizes malate to oxaloacetate, generating NADH but not decarboxylating. Succinate dehydrogenase converts succinate to fumarate, producing FADH2, and also without decarboxylation.

In the TCA cycle, the step that converts isocitrate into α-ketoglutarate involves removing a carboxyl group while also oxidizing the molecule, and this is carried out by isocitrate dehydrogenase. As it oxidizes isocitrate, the enzyme transfers electrons to NAD+, forming NADH, and releases carbon dioxide. This combination of oxidation and decarboxylation is what defines this particular reaction.

Aconitase, instead, just rearranges citrate to isocitrate via an intermediate called cis-aconitate, without removing CO2. Malate dehydrogenase oxidizes malate to oxaloacetate, generating NADH but not decarboxylating. Succinate dehydrogenase converts succinate to fumarate, producing FADH2, and also without decarboxylation.

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