Inosine-monophosphate dehydrogenase; Catalyzes the conversion of inosine 5'-phosphate (IMP) to xanthosine 5'-phosphate (XMP), the first committed and rate-limiting step in the de novo synthesis of guanine nucleotides, and therefore plays an important role in the regulation of cell growth. Belongs to the IMPDH/GMPR family.

Putative nucleotidase YfkN.

Thymidylate synthase A; Catalyzes the reductive methylation of 2'-deoxyuridine-5'- monophosphate (dUMP) to 2'-deoxythymidine-5'-monophosphate (dTMP) while utilizing 5,10-methylenetetrahydrofolate (mTHF) as the methyl donor and reductant in the reaction, yielding dihydrofolate (DHF) as a by- product. This enzymatic reaction provides an intracellular de novo source of dTMP, an essential precursor for DNA biosynthesis.

GMP reductase; Catalyzes the irreversible NADPH-dependent deamination of GMP to IMP. It functions in the conversion of nucleobase, nucleoside and nucleotide derivatives of G to A nucleotides, and in maintaining the intracellular balance of A and G nucleotides; Belongs to the IMPDH/GMPR family. GuaC type 2 subfamily.

Purine nucleoside phosphorylase; The purine nucleoside phosphorylases catalyze the phosphorolytic breakdown of the N-glycosidic bond in the beta- (deoxy)ribonucleoside molecules, with the formation of the corresponding free purine bases and pentose-1-phosphate.

Thymidylate kinase; Phosphorylation of dTMP to form dTDP in both de novo and salvage pathways of dTTP synthesis; Belongs to the thymidylate kinase family.

Xanthine phosphoribosyltransferase; Converts the preformed base xanthine, a product of nucleic acid breakdown, to xanthosine 5'-monophosphate (XMP), so it can be reused for RNA or DNA synthesis.

GMP synthetase; Catalyzes the synthesis of GMP from XMP.

Adenylosuccinate synthetase; Plays an important role in the de novo pathway of purine nucleotide biosynthesis. Catalyzes the first committed step in the biosynthesis of AMP from IMP; Belongs to the adenylosuccinate synthetase family.