title: Multiple forms of nuclear ribonuclease H from Tetrahymena pyriformis.
abstract: Three types of ribonuclease H were detected in the isolated macronuclei of Tetrahymena pyriformis GL, partially purified and characterized. They were eluted at around 0.15 M, 0.3 M and 0.4 M of ammonium chloride in phosphocellulose chromatography, and termed H-1, H-2 and H-3, respectively. The partially purified enzymes have following properties. a) These enzymes specifically hydrolyze the RNA moiety of RNA . DNA hybrid. Neither DNA moiety of RNA . DNA hybrid nor the RNA molecule dissociated by heat from RNA . DNA hybrid is hydrolyzed by these enzymes. b) The enzymes are most active at pH 8.5-9.0. c) They require divalent cations such as Mg2+ or Mn2+ for their activities. The optimal concentrations of these cations are different among these enzymes. d) The mode of cleavage by these enzymes is endonucleoytic, producing mostly oligonucleotides and a small amount of mononucleotides which possess 3'-hydroxyl and 5'-phosphate termini.
mesh_terms: D000645:Ammonium Sulfate / Q000494:pharmacology; D002467:Cell Nucleus / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008970:Molecular Weight; D009994:Osmolar Concentration; D012260:Ribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D012293:Rifampin / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013696:Temperature; D013769:Tetrahymena pyriformis / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D008345:Manganese; D012260:Ribonucleases; D008274:Magnesium; D000645:Ammonium Sulfate; D012293:Rifampin