The de novo and salvage pathways for purine nucleotide
biosynthesis. The pathway of adenosine/inosine toxicity is highlighted.
Dashdot lines indicate the reversible reactions catalyzed by purine
nucleoside phosphorylase (deoD); most strains employed in this study
are null for the enzyme. Dashed lines indicate feedback regulation of
PRPP synthetase by ADP and AMP. The gene designations are: purA,
adenylosuccinate synthetase; purB, adenylosuccinate lyase;
guaB, IMP dehydrogenase; guaA, GMP synthetase;
deoD, purine nucleoside phosphorylase; hpt,
guanine-hypoxanthine phosphoribosyltransferase; gpt, guanine
phosphoribosyltransferase; gsk, guanosine-inosine kinase;
apt, adenine phosphoribosyltransferase; add, adenosine
deaminase; guaC, GMP reductase; prs, PRPP synthetase.