Abstract
Four alkaline ribonucleases [EC 3. 1. 4. 22] were purified 2, 050- to 3, 460-fold from bovine submaxillary gland by repeated CM-Sephadex C-25 chromatography and Sephadex G-50 gel filtration, with a total recovery of about 13%. These were designated as RNase BS1, BS2, BS3, and BS4, based on their order of elution from a CM-Sephadex C-25 column. The molecular weights of these enzymes were estimated by gel filtration to be 19, 000, 17, 500, 17, 000, and 12, 000, respectively. These enzymes are very similar to RNase A in that they are inhibited by heparin, show preferential hydrolysis of C5'-O-P linkages adjacent to a cytosine nucleotide rather than a uracil nucleotide, and in their antigenic properties.
Spermine was found to stimulate the activities of these enzymes; the degree of stimulation was in the order RNase BS4>BS3>BS2>BS1. The stimulation by spermine is due to the increased cleavage of C5'-O-P linkages adjacent to cytosine nucleotide. The reason for the differences in the degree of spermine stimulation of these enzymes is discussed.
