How do ALS inhibitors function as herbicides?

ALS inhibitors, also known as acetolactate synthase inhibitors, function as herbicides by inhibiting a key enzyme in plants. This enzyme, acetolactate synthase, plays a critical role in the biosynthesis of essential amino acids, such as leucine, isoleucine, and valine. When this enzyme is inhibited, the production of these amino acids is disrupted, leading to impaired protein synthesis and ultimately stunting the growth of the plant, or causing its death.

Since these amino acids are vital for the plant's metabolism and development, the inhibition of their synthesis effectively eliminates or controls unwanted weeds while typically having minimal effects on other organisms that do not rely on the same metabolic pathway. This selectivity makes ALS inhibitors useful as herbicides in agricultural practices.