title: Bis-(5'-guanosyl) tetraphosphatase in rat tissues.
abstract: The occurrence and distribution of bis-(5'-guanosyl) tetraphosphatase activity towards dinucleoside tetraphosphates between the 27 000 g supernatant and sedimented fraction were studied in liver, kidney, brain, muscle and intestinal mucosa from rat. The p1p4-bis-(5'-guanosyl) tetraphosphate-hydrolysing activities found in total homogenates were 0.77, 1.44, 0.39, 0.36 and 2.14 units (mumol/min)/g respectively. The activities found in the 27000 g-sedimented fractions were 74, 49, 11, 4 and 96% of those present in the homogenates respectively. The properties of the soluble enzymes were investigated. All of them have low Km values for p1p4-bis-(5'-guanosyl) tetraphosphate (from 2 to 50 microM), are competitively inhibited by guanosine 5'-tetraphosphate with K1 values from 10 to 160 nM, have molecular weights of about 21 000, require Mg2+ or Mn2+ and are inhibited by Ca2+. These properties show that bis-(5'-guanosyl) tetraphosphatase (EC 3.6.1.17), an enzyme previously characterized in Artemia salina and rat liver [Warner & Finamore (1965) Biochemistry 4, 1568-1575; Vallejo, Sillero & Sillero (1974) Biochim, Biophys. Acta 358, 117-125; Lobatón, Vallejo, Sillero & Sillero (1975) Eur. J. Biochem. 50, 495-501], is present in all the rat tissues examined. The inhibition of the enzyme by Ca2+ could be related to the effect of p1p4-bis-(5'-adenosyl) tetraphosphate as a trigger of DNA synthesis [Grummt, Waltl, Jantzen, Hamprecht, Huebscher & Kuenzle (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 6081-6085].
mesh_terms: D017766:Acid Anhydride Hydrolases; D000227:Adenine Nucleotides; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D015226:Dinucleoside Phosphates; D005260:Female; D006159:Guanosine Tetraphosphate / Q000031:analogs & derivatives; D006868:Hydrolysis; D007700:Kinetics; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D013347:Subcellular Fractions / Q000201:enzymology; D014018:Tissue Distribution
chemical_list: D000227:Adenine Nucleotides; D015226:Dinucleoside Phosphates; D006159:Guanosine Tetraphosphate; C015138:diguanosine tetraphosphate; C020733:diadenosine tetraphosphate; D010744:Phosphoric Monoester Hydrolases; D017766:Acid Anhydride Hydrolases; C020023:bis(5'-nucleosyl)tetraphosphatase (asymmetrical); D002118:Calcium