Identification of d-erythro-Dihydroneopterin Triphosphate, the First Product of Pteridine Biosynthesis in Comamonas Sp. (ATCC 11299a)

GTP cyclohydrolase, purified from extracts of Comamonas sp., was shown to convert GTP to formic acid and a single fluorescent compound. The fluorescent product was identified as a dihydroneopterin triphosphate by its absorption spectra and phosphate analysis. After oxidation and dephosphorylation, the d-erythro configuration of the side chain of this dihydroneopterin triphosphate was established by ECTEOLA (epichlorohydrin triethanolamine)-cellulose chromatography and by bioassay using Crithidia fasciculata. The nature of the product was not altered by the presence of the GTP cyclohydrolase-stimulating protein (Cone, J. E., Plowman, J., and Guroff, G. (1974) J. Biol. Chem. 249, 5551). Neopterin cyclic phosphate, previously thought to be an intermediate in the production of pteridine cofactors in Comamonas sp., was found to be an artifact derived from the triphosphate product during paper chromatography in a basic solvent.