Formylglycinamide ribonucleotide amidotransferase from Salmonella typhimurium: role of ATP complexation and the glutaminase domain in catalytic coupling.

Formylglycinamide ribonucleotide (FGAR) amidotransferase (FGAR-AT) takes part in purine biosynthesis and is a multidomain enzyme with multiple spatially separated active sites. FGAR-AT contains a glutaminase domain that is responsible for the generation of ammonia from glutamine. Ammonia is then transferred via a channel to a second active site located in the synthetase domain and utilized to convert FGAR to formylglycinamidine ribonucleotide (FGAM) in an adenosine triphosphate (ATP) dependent reaction.