title: Purification and properties of a new ribonuclease from Aspergillus saitoi.
abstract: From a commercial digestive produced from Aspergillus saitoi, a ribonuclease [EC 3.1.4.23] having a molecular weight of 12,500 has been isolated in addition to the RNase reported previously, which had a molecular weight of 38,000. The enzyme was found to be homogeneous by chromatography on DEAE-cellulose, disc electrophoresis on polyacrylamide gel, and ultracentrifugation. The NH2-terminal amino acid was identified as glutamic acid. The amino acid composition indicated the presence of about 13 tyrosyl residues, 3 histidyl residues, and 2 half-cystine residues. The pH optimum of the RNase was 4.5, using RNA as a substrate. The enzyme was stable on heating at 70 degrees for 5 min from pH 2 to 10. It hydrolysed RNA completely to mononucleotides via 2', 3'-cyclic nucleotides. The rates of release of nucleotides and 2', 3'-cyclic nucleotides were in the order: guanylic acid is greater than adenylic acid is greater than cytidylic acid is greater than uridylic acid.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001230:Aspergillus / Q000201:enzymology*; D002241:Carbohydrates / Q000032:analysis; D002413:Cations, Divalent / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D009712:Nucleotides, Cyclic / Q000378:metabolism; D009994:Osmolar Concentration; D012313:RNA / Q000378:metabolism; D012260:Ribonucleases / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D013696:Temperature
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; D002413:Cations, Divalent; D009712:Nucleotides, Cyclic; D012313:RNA; D012260:Ribonucleases