Characterization of Chicken Red‐Cell RNAase

RNAase from 13‐day‐old chicken‐embryo red cells was purified. Nuclei and cytoplasmic fractions were used as source of the enzyme. The nuclear enzyme was purified 1440‐fold and the one from cytoplasm, 1683‐fold. Both enzyme preparations showed the same optimum pH and ion specificity, but different ionic strength dependence and temperature stability. Kinetic studies with these RNAase fractions indicated that both of them are endonucleases with specificity for pyrimidine nucleotide bases in the substrate, hydrolyzing poly(U) or poly‐(A,U,G) faster than poly(C) or poly(A,C,G). Both enzyme fractions showed strong dependence on the sedondary structure of RNA, and did not hydrolyze single stranded DNA. The implications of these characteristics on the enzyme role are discussed.