ALS catalyzes the first step in the synthesis of the branched-chain amino acids (valine, leucine, and isoleucine).

[3] A human protein of yet unknown function, sharing some sequence similarity with bacterial ALS, is encoded by the ILVBL (ilvB-like) gene.

[7] The structure of acetolactate synthase that was used for the picture on this page was determined using X-ray diffraction at 2.70 angstroms.

[8] In several experiments, it has been shown that mutated strains of Escherichia coli K-12 without the enzyme were not able to grow in the presence of only acetate or oleate as the only carbon sources.

Each subunit pair, or ALS I, II, and III respectively, is located on its own operon, ilvBN, ilvGM and ilvIH (where ilvN regulated ilvB, and vice versa).

[16] The ilvGMEDA operon encodes the ilvGM (ALS II) pair as well as a branched-chain-amino-acid transaminase (ilvE), dihydroxy-acid dehydratase (ilvD), and threonine ammonia-lyase (ilvA).

Both the ilvGMEDA and ilvBNC operons are derepressed during shortages of the branched-chain amino acids by the same mechanism that represses them.

[17][18] Inhibitors of ALS are used as herbicides that slowly starve affected plants of these amino acids, which eventually leads to inhibition of DNA synthesis.

Therefore resistance mutations are expected to have widely varying effects on normal ALS catalysis activity, positive, negative and neutral.

Unsurprisingly that is exactly what experiments have shown, including Yu et al., 2007 finding resistance in Hordeum murinum due to a proline→serine substitution at amino acid 197 to increase ALS activity by 2x-3x.

[2] CADASIL, an identified autosomal dominant condition characterized by the recurrence of subcortical infarcts leading to dementia, was previously mapped to “ILVBL” gene within a 2-cM interval, D19S226–D19S199.

No recombination event was observed with D19S841, a highly polymorphic microsatellite marker isolated from a cosmid mapped to this region.

[4] In the study of Escherichia coli, the FAD binding domain of ilvB has been shown to interact with ilvN and activate the AHAS I enzyme.