Acetolactate

Acetolactate is a carboxylic acid with the chemical formula C6H10O5. It is an intermediate in the metabolic pathway known as the valine, leucine and isoleucine biosynthesis pathway. Acetolactate is produced from pyruvate by the enzyme acetolactate synthase.

Structure and properties

Acetolactate is a chiral molecule, meaning it has a non-superimposable mirror image. It exists in two enantiomeric forms, (R)-acetolactate and (S)-acetolactate. The (S)-enantiomer is the biologically active form.

Biosynthesis

In the valine, leucine and isoleucine biosynthesis pathway, acetolactate is produced from two molecules of pyruvate by the enzyme acetolactate synthase. This is the first step in the pathway, and is a key regulatory point. The enzyme is inhibited by the end products of the pathway, valine, leucine and isoleucine, in a process known as feedback inhibition.

Role in brewing

Acetolactate is also an important intermediate in the production of beer. During fermentation, yeast produces acetolactate, which is then converted to diacetyl. Diacetyl gives beer a buttery flavor, which is undesirable in large amounts. Brewers therefore try to minimize the production of acetolactate to prevent the formation of diacetyl.

See also

• Acetolactate synthase
• Valine, leucine and isoleucine biosynthesis
• Diacetyl

Acetolactate Resources
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