Highly purified p53 protein from different sources was able to degrade DNA with a 3'-to-5' polarity, yielding deoxynucleoside monophosphates as reaction products. This exonuclease activity was dependent on Mg2+ and inhibited by addition of 5 mM nucleoside monophosphates. This exonuclease activity is intrinsic to the wild-type p53 protein: it copurified with p53 during p53 preparation; only puri...

Several laboratories have reported studies on individual enzymes that belong to the general class of adenosine triphosphate : nucleoside monophosphate phosphotransferases (EC 2.7.4.4), commonly termed nucleoside monophosphate kinases (l-7). Studies with partially purified enzyme preparations have indicated that a variety of nucleoside monophosphates can serve as alternative substrates for nucle...

5'-nucleotidases (EC 3.1.3.5) catalyze the hydrolytic dephosphorylation of 5'-ribonucleotides and 5'-deoxyribonucleotides as well as complex nucleotides, such as uridine 5'-diphosphoglucose (UDP-glucose), nicotinamide adenine dinucleotide and flavin adenine dinucleotide, to their corresponding nucleosides plus phosphate. These enzymes have been found in diverse species in intracellular and memb...

The catabolism of GTP and ATP in intact human thymocytes was studied, and the effect of intracellular Pi concentrations on various catabolic reactions was evaluated. Induction of nucleotide catabolism was performed with either NaN3 or deoxyglucose. NaN3 induced an increase in intracellular Pi, whereas deoxyglucose induced a decrease in Pi in human thymocytes. At elevated Pi concentrations, an i...

Ethidium and isometamidium induce the breakdown of intracellular adenosine triphosphate in Ehrlich ascites tumor cells incubated in vitro. Ethidium induces appreciable adenosine triphosphate breakdown only when cells are incubated without glucose, whereas isometamidium produces this effect both in the presence and absence of glucose. In cells treated with isometamidium, purine nucleoside monoph...

5'-nucleotidases catalyze the hydrolytic dephosphorylation of nucleoside monophosphates. As catabolic enzymes they contribute significantly to the regulation of cellular nucleotide levels; misregulation of nucleotide metabolism and nucleotidase deficiencies are associated with a number of diseases. The seven human 5'-nucleotidases differ with respect to substrate specificity and cellular locali...

Ordinarily packaged in DNA, adenine deoxyribonucleotides are preferentially concentrated in erythrocyte and lymphocyte cytosol in adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) deficiency. A spectrum of cytosol enzyme activities are defined in terms of reaction velocities, K0.5s, and nucleotide partition after incubation with ribo- and deoxyribonucleotides. AMP and dAMP were dephosp...

RNase R is a highly processive, hydrolytic 3'-5' exoribonuclease belonging to the RNB/RNR superfamily which plays significant roles in RNA metabolism in bacteria. The enzyme was observed to be essential for growth of the psychrophilic Antarctic bacterium Pseudomonas syringae Lz4W at a low temperature. We present results here pertaining to the biochemical properties of RNase R and the RNase R-en...