TrpG

trpG is a gene that encodes the glutamine amidase subunit of the enzyme pair known as anthranilate synthase, which is involved in the early steps of tryptophan biosynthesis in many bacteria. In the common bacterial form, anthranilate synthase is a heterotetramer composed of two TrpE subunits and two TrpG subunits. TrpG supplies the ammonia generated from glutamine, which is used by the TrpE subunit to convert chorismate into anthranilate, the first dedicated intermediate toward tryptophan.

The TrpG protein belongs to the class of glutamine amidotransferases and provides the glutamine hydrolysis activity necessary for the reaction. The enzyme’s activity is typically coordinated with TrpE, and together the subunits regulate the flow of intermediates through the tryptophan biosynthesis pathway. In many organisms, the activity of anthranilate synthase is subject to regulation by feedback from tryptophan itself, helping to balance amino acid production with cellular demand.

Genetic and physiological context: trpG is commonly found within the broader trp biosynthetic gene cluster or operon in bacteria, sometimes alongside trpE and other trp genes. Expression and flux through the pathway can be modulated by physiological tryptophan levels and by regulatory mechanisms such as attenuation in some species. Mutations in trpG can disrupt tryptophan synthesis, often resulting in a requirement for exogenous tryptophan or anthranilate for growth.

Distribution and relevance: trpG homologs are widespread among bacteria and are a key part of the conserved tryptophan biosynthesis pathway. The gene is of interest in studies of amino acid metabolism, operon regulation, and metabolic engineering.