ALS_ss_C is the C-terminal half of a family of proteins which are the small subunits of acetolactate synthase. Acetolactate synthase is a tetrameric enzyme, containing probably two large and two small subunits, which catalyses the first step in branched-chain amino acid biosynthesis. This reaction is sensitive to certain herbicides [1].

1: Identification of an acetolactate synthase small subunit gene in two eukaryotes. Duggleby RG; Gene. 1997;190:245-249. PMID:9197540