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Purification from normal human plasma and biochemical characterization of a ribonuclease specific for poly(C) and
Irini D Leimoni1, Diamantis C Sideris, Emmanuel G Fragoulis
1Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Athens, Panepistimioupolis, Greece.
Abstract:
A new specific ribonuclease from normal human plasma has been purified to homogeneity, following a five-step purification protocol that included DEAE-Sepharose, CM-Sepharose, and Heparin-Sepharose chromatographies. The purified enzyme was found to be glycosylated and appeared as a single 25-kDa band on a SDS polyacrylamide gel. This RNase is poly(C) preferential, degrading poly(U) at a lower rate. Activity of this RNase toward cleavage of native substrates such as ribosomal RNA was also detected. The human plasma ribonuclease is a thermolabile molecule, exhibiting maximum activity at pH 6.5. Comparison between other known plasma RNases and the human plasma ribonuclease described here indicated a variety of differences in their biochemical and catalytic properties.