title: The purification and properties of chicken liver RNase: An enzyme which is useful in distinguishing between cytidylic and uridylic acid residues.
abstract: A heat-stable endoribonuclease isolated from chicken liver has been purified to homogeneity as evidenced by the presence of a single protein band upon polyacrylamide gel electrophoresis. The enzyme can, in limit digests of 5 S rRNA and 5.8 S rRNA, dinstinguish between cytidylic and uridylic acids bonds at a ratio of 61:1 and, therefore, may be useful in RNA sequence analysis. The means by which the enzyme hydrolyzes substrate is unusual in that kinetic data do not support a simple formation and breakdown of an enzyme . substrate complex. Rather, the existence of a second complex, consisting of 2 mol of substrate and one of enzyme, derived from the initial enzyme . substrate complex, is postulated. In common with the other endonucleases, enzyme activity is inhibited by free poly(A) or tracts of the polypurine present at the 3'-terminus of RNA. Reversal of inhibition and restoration of activity may be achieved by the addition of low concentrations of spermidine to reaction mixtures.
mesh_terms: D000818:Animals; D002412:Cations; D002645:Chickens; D003568:Cytidine Monophosphate / Q000032:analysis; D004720:Endonucleases / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D011700:Putrescine / Q000494:pharmacology; D012260:Ribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology; D013379:Substrate Specificity; D014542:Uridine Monophosphate / Q000032:analysis
chemical_list: D002412:Cations; D013096:Spermine; D014542:Uridine Monophosphate; D004720:Endonucleases; D012260:Ribonucleases; D003568:Cytidine Monophosphate; D013095:Spermidine; D011700:Putrescine