Azaserine

Azaserine is an antibiotic that is a potent inhibitor of purine nucleotide synthesis. Azaserine is similar in structure to glutamine and is an irreversible inhibitor of glutamine amidotransferases, which catalyze the ATP-dependent transfer of the amido nitrogen of glutamine to an acceptor. Four such reactions occur in nucleotide synthesis.

See also: Nucleotides, Amino Acids Not In Proteins, De Novo Biosynthesis of Purine Nucleotides (from Chapter 22)