The yeast Cdc8 exhibits both deoxythymidine monophosphate and diphosphate kinase activities

The existence of multifunctional enzymes in the nucleotide biosynthesis pathways is believed to be one of the important mechanisms to facilitate the synthesis and the efficient supply of deoxyribonucleotides for DNA replication. Here, we used the bacterially expressed yeast thymidylate kinase (encoded by the CDC8 gene) to demonstrate that the purified Cdc8 protein possessed thymidylate-specific nucleoside diphosphate kinase activity in addition to thymidylate kinase activity. The yeast endogenous nucleoside diphosphate kinase is encoded by YNK1, which appears to be non-essential. Our results suggest that Cdc8 has dual enzyme activities and could duplicate the function of Ynk1 in thymidylate synthesis. We also discuss the importance of the coordinated expression of CDC8 during the cell cycle progression in yeast.     

Enzymes of deoxythymidine triphosphate biosynthesis in Neurospora crassa mitochondria.

Intact mitochondria of Neurospora crassa incorporate deoxythymidine 5'-monophosphate (dTMP) into deoxyribonucleic acid but not the label from (methyl-3H) deoxythymidine. Mitochondrial homogenates contain deoxythymidylate kinase (EC 2.7.4.9), deoxycytidylate aminohydrolase (dCMP deaminase) (EC 3.5.4.12), and thymidylate synthetase (EC 2.1.1b), but not thymidine kinase (EC 2.7.1.21) activity. dTMP kinase is loosely bound to the mitochondrial membrane and is solubilized by 0.4 M KCl in mitochondrial homogenates, the dCMP aminohydrolase deaminase) is bound to the inner membrane and is not solubilized by 0.4 M KCl. dTMP synthetase activity is found in the 2,000 times g particulate fractions by homogenization of mitochondria in 0.4 M KCl. The dCMP deaminase activity found in the particulate fraction of the inner membrane is efficiently regulated by the products of the pathway: deoxycytidine 5'-triphosphate activates whereas deoxythymidine 5'-triphosphate inhibits, as found for the soluble enzyme from other sources. These data indicate that mitochondria of N. crassa contain specific enzymes for the biosynthesis of deoxythymidine triphosphate.     

The prebiotic synthesis of deoxythymidine oligonucleotides

Summary A reaction shown to oligomerize nucleotides under possible prebiotic conditions has been made more plausible by the finding that the reaction can proceed at initial neutral pH in the presence of acid salts or NH₄Cl.     

The prebiotic synthesis of deoxythymidine oligonucleotides

A reaction which oligomerizes nucleotides under possible prebiotic conditions has been characterized. Nucleoside monophosphate in the presence of cyanamide at acid pH condenses to form dithymideine pyrophosphate and phosphodiester bonded compounds. Imidazole compounds and activated precursors such as nucleoside triphosphate are not necessary for this ologomerization reaction which produces primarily cyclic ologonucleotides.     

Mechanism of the enzymatic reaction catalyzed by uridine diphosphate glucose dehydrogenase. The chemical synthesis of uridine diphosphate glucose-6-H3 and its oxidation by uridine diphosphate glucose dehydrogenase]

The synthesis of UDP-glucose-6-s-H was performed through condensation of alpha-D-glucopyranosyl phosphate-6-3-H and uridine 5'-phosphomorpholidate. Enzymic oxidation of UDP-glucose-6-3-H with calf liver UDP-glucose dehydrogenase was found to proceed with direct transfer of the hydrogen from C-6 of UDP-glucose onto NAD.