Isolation and characterization of two alkaline ribonucleases from calf serum

Purification and characterization of a novel poly(U), poly(C) ribonuclease from Saccharomyces cerevisiae

A new ribonuclease from Saccharomyces cerevisiae, specific for poly(U) and poly(C) substrate, was purified near to homogeneity by successive fractionation with DEAE-Sepharose, Heparin-Sepharose and CM-Sepharose chromatography. The purified molecule detected by SDS/polyacrylimide gel electrophoresis has a molecular mass of 29 kDa. The optimum pH for the enzyme activity is 5.5-7 and its isoelectric point is 7.5. The purified enzyme was able to degrade 26S, 18S and 5S rRNAs as well as mRNA obtained from in vitro transcription. No catalytic activity was observed when the RNase was incubated with tRNA and double stranded substrate. Our findings suggest that this novel RNase may play an important role in the processing of RNA in Saccharomyces cerevisiae.

Structure of the bovine pancreatic ribonuclease gene: the unique intervening sequence in the 5' untranslated region contains a promoter-like element

Although pancreatic ribonucleases are extensively studied proteins, little information is available on nucleic acids coding for these enzymes. Here, for the first time, the structure of a gene coding for such an enzyme, the well known bovine pancreatic ribonuclease, is reported. The coding region of this gene is devoid of introns, whereas the 5' untranslated sequence of the pancreatic transcript contains an intron of 735 nucleotides. This intervening sequence is endowed with signals (CAAT and TATA boxes) which might act as regulatory elements. The structural organization of this gene suggests that the sequence coding for the bovine pancreatic ribonuclease might be expressed under the control of two different promoters.

Production of two phosphatases by Lysobacter enzymogenes and purification and characterization of the extracellular enzyme

Lysobacter enzymogenes produces an extracellular phosphatase (EC. 3.1.3.1) during the stationary phase of growth. The cells also produce a cell-associated alkaline phosphatase. This enzyme is found in the particulate fraction of cell extracts and may be membrane bound. The production of both phosphatases, especially the extracellular enzyme, is reduced by inorganic phosphate. The extracellular phosphatase was purified to a specific activity of 270 U/mg primarily by chromatography on carboxymethyl cellulose and gel filtration. The enzyme is stable under normal storage conditions but is rapidly inactivated above 70 degrees. It consists of one polypeptide with an approximate molecular weight of 25,000. The pH optimum is 7.5, and the Km for p-nitrophenylphosphate is 2.2 X 10(-4) M. The enzyme degrades a number of other phosphomonoesters but at a reduced rate compared with the rate obtained with p-nitrophenylphosphate. Phosphate and arsenate inhibit the enzyme, but EDTA and other chelating agents have no effect. The lack of a metal ion requirement for activity, the lower molecular weight, the soluble nature of the enzyme, and the lower pH optimum clearly distinguish the extracellular phosphatase from the cell-associated phosphatase and from other bacterial phosphatases.

The ribonucleases of bovine skeletal muscle

Bovine skeletal muscle contains small amounts of at least six heat- and acid-stable RNA-degrading enzymes. Our results are the first evidence for multiple ribonucleases in skeletal muscle. Three of these have been highly purified, and each has been shown to be a pyrimidine-specific endoribonuclease by use of a rapid sequencing technique employing gel electrophoresis. However, synthetic co-polymers containing adenylate or guanylate residues in addition to pyrimidine residues are hydrolysed at higher rates than are the pyrimidine homopolymers. With 0.63 mM yeast RNA as substrate, all three enzymes (ribonucleases I, II and III) are optimally active in alkaline solution (pH 7.5-8.5) containing 0.05-0.15 M univalent salts, do not require bivalent cations, and have molecular weights of 13 000-20 000. The properties of muscle ribonuclease I are very similar to those of bovine pancreatic ribonuclease A. Muscle ribonucleases II and III have characteristics similar to those of ribonucleases found in various other bovine tissues. In common with all previously studied pyrimidine-specific endoribonucleases, the bovine muscle ribonucleases are inhibited by such purine homopolynucleotides as polyadenylate. Furthermore, polyamines, present in low concentrations, can reverse or regulate the amount of inhibition of enzyme activity.

Purification and properties of a ribonuclease induced during the early larval development of Artemia salina

Dormant gastrulae and developing embryos of the brine shrimp Artemia salina contain very low levels of nuclease activity. During early larval development, there is an induction of ribonuclease which has been partially purified and characterized. The enzyme catalyzes an endonucleolytic cleavage of RNA and has no detectable activity on native or denatured DNA. Among a series of synthetic polynucleotides, poly(U) is hydrolyzed with the highest efficiency and poly(G) is not cleaved by the enzyme. The activity on poly(U) is 100 times higher than on RNA. The enzyme requires Mg2+ or Mn2+ and in inactivated by treatment with chelating agent. The inactive preparations can be reactivated by Ca2+ and Mn2+ but not by Mg2+. The ribonuclease is thermosensitive and has maximal activity at pH 7.5. These properties distinguish the Artemia salina ribonuclease from other eukaryotic ribonucleases already reported. The high activity and specificity of this ribonuclease on poly(U) may suggest a role for this enzyme in the processing of the messenger RNA.

Epidermal nucleases. III. The ribonucleases of human epidermis

Sodium acetate and sulphuric acid extracts of human epidermis can each be separated by chromatographic techniques into three or more fractions with ribonuclease activity. Eight of these fractions were compared with respect to molecular weight, pH activity profile, polyribonucleotide hydrolysis, and activity in the presence of low levels of spermidine. Sodium acetate and sulphuric acid extracts were also prepared from callus and from psoriatic lesions and compared with extracts from normal epidermis for their response to exogenous spermidine. All eight human epidermal ribonuclease fractions studied had an apparent molecular weight of 15,000 daltons. Seven of the ribonuclease fractions were optimally active at alkaline pHs (pH 7.3-7.6 in sodium phosphate and pH 8.I in Tris-HCl) while the eighth ribonuclease was most active at pH 5.6 in a citrate-phosphate buffer. All enzymes hydrolyzed polycytidylic acid and five also hydrolyzed polyuridylic acid. None hydrolyzed polyadenylic acid. Seven of the eight ribonucleases studied exhibited greater activity in the presence of added spermidine. The extracts from psoriatic scales showed markedly elevated ribonuclease levels which could not be raised further by the addition of spermidine.