In the present study, activities of ribonucleases (RNase) present in normal human serum were determined at acidic (pH 6.0) and neutral (pH 7.5) media using polyribonucleotides as substrate. The RNases in normal human serum were separated by DEAE-cellulose chromatography and their properties were partially characterized.
Both acid and neutral RNases in normal human serum exhibited the highest activity against polycytidylate (poly C) and the lowest activity against purine ribonucleotides, the decreasing order of the activity.being that measured with poly C, polyuridylate, RNA, polyadenylate and polyguanylate, respectively. These results indicated that the RNases in normal human serum showed grater affinity to the phosphodiester bonds involving pyrimidine bases especially cytosine. DEAE-cellulose chromatographical analysis for the RNases revealed that normal human serum did contain at least three types of RNases: RNase active against, both RNA and poly C; RNase active against RNA; RNase active against poly C.
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