Conversion of the antithyroid drug 2-thiouracil to 2-thio-5'-UMP by UMP pyrophosphorylase

Structural analysis of an iron-assisted carbon monolayer for delivery of 2-thiouracil

An idea of employing an iron-assisted carbon (FeC) monolayer for delivery of 2-thiouracil (2TU) was examined in this work by analyzing structural features for singular and bimolecular models. Density functional theory (DFT) calculations were performed for optimizing the structures and evaluating molecular and atomic descriptors for analyzing the models systems. Two bimolecular models were obtained assigning by S-FeC and O-FeC models, in which each of S and O atom of 2TU was relaxed towards the Fe region of FeC surface in the mentioned models, respectively. The results indicated that both models were achievable with slightly more favorability for formation of S-FeC model. The obtained molecular orbital properties revealed the dominant role of FeC monolayer for managing future interactions of attached 2TU, which is indeed a major role for employing nanomaterials for targeted drug delivery purposes. In addition to energies and molecular orbital features, atomic quadrupole coupling constants indicated the benefit of employing FeC monolayer for drug delivery of 2TU.

Characterisation of a partially purified uracil phosphoribosyltransferase from the opportunistic pathogen Candida albicans

This paper describes for the first time the partial purification and properties of uracil phosphoribosyltransferase (UPRTase) from the yeast Candida albicans. UPRTase was purified 38 fold by acid precipitation, DEAE-Sephacel chromatography and ultrafiltration. Further purification of UPRTase was unsuccessful due to the labile nature of the enzyme and the failure in obtaining satisfactory stabilizing conditions. SDS-PAGE suggested that the enzyme exists as a dimer of two dissimilar subunits with molecular masses of 47 and 38 kDa. The pH optimum for phosphoribosylation was about 7.5 and the optimal Mg++ concentration was 2 mM. The kinetics of the enzymes for its substrates, uracil and 5-phosphoribosyl-1-pyrophosphate (PRPP) were determined by measuring initial enzyme velocities over a wide range of concentrations of either substrate at different fixed concentrations of the second substrate. Graphic analysis of the data by Hanes-Woolf plots indicated that the reaction is indistinguishable from a double displacement reaction. 'Ping pong' mechanism has been previously reported for other phosphoribosyltransferases. The enzyme has a low affinity for its substrates (Km = 70.5 and 186 microM for uracil and PRPP, respectively) as compared with those of E. coli and baker's yeast. Inhibition studies indicate that 5-fluorouracil acts as an alternative substrate for UPRTase with 1.6 times higher specific activity.

Structural features of the phosphoribosyltransferases and their relationship to the human deficiency disorders of purine and pyrimidine metabolism

Similarities in the physical and chemical properties of the phosphoribosyltransferase family of enzymes suggest that they may share common structural features as observed in other functionally related proteins. The unusually high incidence of structural gene mutations of these enzymes in man are associated with several metabolic diseases of purine and pyrimidine metabolism. It is proposed that these disorders are the consequence of structural mutations to an architectural domain common to all of the phosphoribosyltransferases.