- Acetolactate synthase
protein
Name=(Bacterial acetolactate synthase)-like
caption=
width=
HGNCid=6041
Symbol=ILVBL
AltSymbols=
EntrezGene=10994
OMIM=605770
RefSeq=NM_176826
UniProt=Q99651
PDB=
ECnumber=2.2.1.6
Chromosome=19
Arm=p
Band=13.1
LocusSupplementaryData=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 , andisoleucine ).Inhibitors of ALS are used as herbicides that slowly starve affected plants of these
amino acid s, 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).Regulation
Acetolactate synthase consists of three pairs of subunits. Each pair includes a large subunit, which is thought to be responsible for
catalysis , and a small subunit forfeedback inhibition . Each subunit pair is located on its ownoperon . Together, these operons code for several enzymes involved in branched-chain amino acid biosynthesis. Regulation is different for each operon.The "ilvGMEDA" operon (encoding ALS II,
branched-chain-amino-acid transaminase ,dihydroxy-acid dehydratase , andthreonine ammonia-lyase ) is regulated byfeedback inhibition in the form oftranscriptional attenuation . That is, transcription is reduced in the presence of the pathway's end products, the branched-chain amino acids.The "ilvBNC" operon, which encodes ALS I and a
ketol-acid reductoisomerase , is similarly regulated, but is specific to isoleucine and leucine; valine does not affect it directly.Both the "ilvGMEDA" and "ilvBNC" operons are derepressed during shortages of the branched-chain amino acids by the same mechanism that represses them. Both of these operons as well as the third, "ilvIH", are regulated by
leucine-responsive protein (Lrp).External links
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