Acid protease

Acid protease is a type of enzyme that breaks down proteins. It is active mainly in acidic environments, such as those containing acetic acid, and it breaks proteins down into smaller peptides, which are fragments made up of 2 to 20 amino acids linked together. However, acid protease does not produce free amino acids themselves; it mainly forms peptides. In this way, it contributes to the formation of flavor and aroma components during sake brewing and fermentation.