When transaminated, the three branched-chain amino acids (valine, leucine, and isoleucine) form compounds that have the characteristic odor of maple syrup. An enzyme known as branched-chain α-keto acid dehydrogenase converts these compounds into CoA esters. People who do not have this enzyme have the genetic disease known as maple syrup urine disease-so-called because their urine smells like maple syrup.
a. Give the structures of the compounds that smell like maple syrup.
b. Give the structures of the CoA esters.
c. Branched-chain α-keto acid dehydrogenase has five coenzymes. Identify them.
d. Suggest a way to treat maple syrup urine disease.