guanosine-tetraphosphate and adenosine-5--tetraphosphate

A new, straightforward, reliable, and convenient protection-free one-pot method for the synthesis of 2'-deoxynucleoside-5'-tetraphosphate and ribonucleoside-5'-tetraphosphate is reported. The present synthetic strategy involves the monophosphorylation of a nucleoside followed by reaction with tris-(tri-n-butylammonium) triphosphate and subsequent hydrolysis of the putative cyclic tetrametaphosphate intermediate to provide nucleoside-5'-tetraphosphate in moderate yield with high purity. A plausible mechanism is proposed to account for the formation of product.

Topics: Adenine Nucleotides; Dinucleoside Phosphates; Guanosine Tetraphosphate; Hydrolysis; Phosphorylation; Polyphosphates; Uracil Nucleotides

A cytosolic preparation of Saccharomyces cerevisiae is capable of hydrolyzing adenosine-5'-tetraphosphate and guanosine-5'-tetraphosphate with activities which are 1.5-2 times greater than that with polyP15. The apparent K(m) values for hydrolysis of adenosine-5'-tetraphosphate and guanosine-5'-tetraphosphate are 100 and 80 microM, respectively. A comparative study of inhibitors shows that these activities are inherent characteristics of these exopolyphosphatases.

Topics: Acid Anhydride Hydrolases; Adenine Nucleotides; Cytosol; Enzyme Inhibitors; Guanosine Tetraphosphate; Heparin; Hydrolysis; Kinetics; Saccharomyces cerevisiae; Sodium Fluoride

1. An enzyme has been partially purified from Ehrlich ascites tumour cells which specifically hydrolyses dinucleosidetetraphosphates, with Km values of around 2 microM. The products of the hydrolysis are the corresponding nucleoside tri- and monophosphates. Dinucleoside Tri- and diphosphates were not substrates of the reaction. 2. The enzyme requires Mg2+ or Mn2+, is maximally active at a pH value of approx. 7.5 and has a mol, wt of 19,800 as estimated by filtration on Sephadex G-75. Nucleoside mono-, di- and triphosphates were competitive inhibitors of the reaction with Ki values in the 0.1 mM range. 3. Particularly relevant is the inhibition of this enzyme by adenosine and guanosine 5'tetraphosphates. In the course of this investigation, the presence of uridine 5'-tetraphosphate was detected in a commercial preparation of UTP. Adenosine, guanosine and uridine 5'-tetraphosphates were very strong inhibitors of the reaction with Ki values in the nM range.

Topics: Acid Anhydride Hydrolases; Adenine Nucleotides; Animals; Carcinoma, Ehrlich Tumor; Chromatography, DEAE-Cellulose; Guanine Nucleotides; Guanosine Tetraphosphate; Mice; Nucleotides; Phosphoric Monoester Hydrolases; Substrate Specificity; Uracil Nucleotides