Identification of two alpha-ketoglutarate-dependent dioxygenases in extracts of Rhodotorula glutinis catalyzing deoxyuridine hydroxylation.

Attempts to isolate deoxyuridine 2'-hydroxylase from Rhodotorula glutinis by the procedure of Warn-Cramer et al. (Warn-Cramer, B. J., Macrander, L. A., and Abbott, M. T. (1983) J. Biol. Chem. 258, 10551-10557) have led to the identification and partial purification of a newly recognized alpha-ketoglutarate-requiring oxygenase. This activity, designated deoxyuridine (uridine) 1'-hydroxylase, in the presence of iron and ascorbate, catalyzes the conversion of deoxyuridine (uridine), O2, and alpha-ketoglutarate to uracil, deoxyribonolactone (ribonolactone), CO2, and succinate. Incubation of [1'-3H]uridine with this activity results in time-dependent formation of uracil concomitant with production of CO2 and 3H2O. No Vmax/Km isotope effect is observed on this reaction. Uracil production is accompanied by stoichiometric production of ribonolactone identified by NMR spectroscopy. Also reported in this paper is the partial purification and characterization of the alpha-ketoglutarate-requiring enzyme, deoxyuridine 2'-hydroxylase. Incubation of [2'-alpha-3H]deoxyuridine with this activity results in concomitant production of uridine and 3H2O. Incubation with [2'-beta-3H] deoxyuridine results in the production of uridine whose specific activity is identical to that of the starting material. This enzyme catalyzes the conversion of deoxyuridine to uridine with retention of configuration. No isotope effect is observed on this transformation.