Deregulation of glutamine PRPP amidotransferase activity

A method for purine nucleotide biosynthesis, said method comprising the step of culturing a host cell in a medium suitable for purine nucleotide biosynthesis, said host cell transformed with a nucleic acid sequence encoding a modified E. Coli glutamine PRPP amidotransferase, wherein the amino acid sequence of said modified E. Coli amidotransferase differs from the amino acid sequence of a native E coli glutamine PRPP amidotransferase in that one or more amino acid residues of said modified amidotransferase are substituted at positions equivalent to the amino acid positions in the Bacillus amidotransferase selected from the group consisting of 282, 283, 307, and 347 of SEQ ID NO:1 with amino acids not native to said position or positions, wherein said equivalent positions are identified based on comparison of amino acid sequences of Bacillus and E. Coli glutamine PRPP amidotransferases, and wherein said modified E. coli amidotransferase is less sensitive to end-product inhibition than is the native E. coli glutamine PRPP amidotransferase.