tetrahydrouridine and pyrimidin-2-one-beta-ribofuranoside

Pentatricopeptide repeat (PPR) proteins with C-terminal DYW domains are present in organisms that undergo C-to-U editing of organelle RNA transcripts. PPR domains act as specificity factors through electrostatic interactions between a pair of polar residues and the nitrogenous bases of an RNA target. DYW-deaminase domains act as the editing enzyme. Two moss (

Topics: Adenosine Triphosphate; Biocatalysis; Bryopsida; Cytidine; Cytosine; Ions; Magnesium; Mutation; Plant Extracts; Plant Proteins; Protein Aggregates; Protein Domains; Protein Multimerization; Recombinant Proteins; Repetitive Sequences, Amino Acid; RNA Editing; Substrate Specificity; Temperature; Tetrahydrouridine; Uracil; Zea mays; Zinc

Deamination of the nucleoside analogues ARA-C and 5-AZA-CdR by CR deaminase results in a loss of antileukemic activity. To prevent the inactivation of these analogues, inhibitors of CR deaminase may prove to be useful agents. In the present study we investigated the effects of the deaminase inhibitors Zebularine, 5-F-Zebularine, and diazepinone riboside on the deamination of CR, ARA-C, and 5-AZA-CdR using highly purified human CR deaminase (EC 3.5.4.5). These inhibitors produced a competitive type of inhibition with each substrate, the potency of which followed the patterns diazepinone riboside greater than 5-F-Zebularine and THU greater than Zebularine. 5-AZA-CdR was more sensitive than ARA-C to the inhibition produced by these deaminase inhibitors. The inhibition constants for diazepinone riboside lay in the range of 5-15 nM, suggesting that this inhibitor could be an excellent candidate for use in combination chemotherapy with either ARA-C or 5-AZA-CdR in patients with leukemia.

Topics: Antineoplastic Agents; Azacitidine; Azepines; Cytarabine; Cytidine; Cytidine Deaminase; Deamination; Decitabine; Humans; Kinetics; Pyrimidine Nucleosides; Tetrahydrouridine