[Specificity of synthetic polyribonucleotides hydrolysis by endoribonuclease from cobra (Naja oxiana) venom].

An analysis of kinetic differences in homopolyribonucleotides hydrolysis by cobra venom endoribonuclease was carried out. It was concluded that the rate and intensity of hydrolysis as well as the length of the linear parts of the kinetic curves are correlated with the content of the nucleotide units with the C3'-endo conformation in the substrates. The structure factor was shown to predominate in some cases over the temperature factor. Protamine sulfate inhibits the enzyme by blocking its phosphodiether bonds. Study on the effects of divalent metal ions demonstrated the possibility that the enzyme-Me2+ complex is functionally active and that the ion-free polyribonucleotides are true substrates.