It is a forum rule (see red link above) that you must show your attempt at solving a problem before we can help you. However, I will give you a small hint. A mutation in α-ketoglutarate dehydrogenase would affect the fate of this compound, but the question is asking you about α-ketoglutarate itself. In other words, you may be confusing yourself unnecessarily about the mutation issue. I would start by drawing out the reactions.