Acetolactate synthase

The acetolactate synthase (ALS) enzyme (also known as acetohydroxy acid synthase, or AHAS) is the first step in the synthesis of the branched-chain amino acids (valine, leucine, and isoleucine).

These herbicides slowly starve affected plants of these amino acids which eventually leads to inhibition of DNA synthesis.

They affect grasses and dicots alike.

The ALS inhibitor family includes sulfonylureas (SUs), imidazolinones (IMIs), triazolopyrimidines (TPs), pyrimidinyl oxybenzoates (POBs), and sulfonylamino carbonyl triazolinones (SCTs).