Acetyl coenzyme from leucine

Higher alcohol production by yeasts appears to be linked not only to the catabolism of amino acids but also to their synthesis via the corresponding ketonic acids. These acids are derived from the metabolism of sugars. For example, propan-l-ol has no corresponding amino acid. It is derived from a-ketobutyrate which can be formed from pyruvate and acetyl coenzyme A. a-Ketoisocaproate is a precursor of isoamylic alcohol and an intermediary product in the synthesis of leucine. It too can be produced from a-acetolactate, which is derived from pyruvate. Most higher alcohols in wine can also be formed by the metabolism of glucose without the involvement of amino acids. 

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