In this class, 6 and 13 proteins from the mid-exponential and early stationary growth phases, respectively, were found to be involved inpurine ribonucleotide de novo biosynthesis (GMP synthase, IMP dehydrogenase, and adenylosuccinate synthase), pyrimidine ribonucleotide de novo biosynthesis (carbamoyl phosphate synthase, orotate phosphoribosyl-transferase, and uridylate kinase), the salvage of nucleosides and nucleotides (adenylate kinase, phosphopentomutase, ribose-phosphate
pyrophosphokinases, and uracil phosphoribosyltransferase), and sugar-nucleotide biosynthesis and interconversion (dTDP-glucose-4,6-dehydratase, glucose-1phosphate thymidylyltransferase).