Purification of two ribonucleases from macrophage culture medium and studies on their effect on granulation-tissue fibroblasts.

Two ribonuclease activities have been isolated from macrophage culture medium. SDS-electrophoresis gave a molecular weight of 26,000 for both RNAases. The two RNAases differ only slightly in their enzymic properties. They are optimally active at neutral and slightly alkaline pH, and are not activated by monovalent or divalent cations or by spermine. Cu(II), Zn(II), Mn(II) and heparine inactivate them but they are not affected by the RNAase inhibitor from rat liver. They both degrade RNA endonucleolytically to mono- and oligonucleotides. They react to synthetic polynucleotides, especially poly(C), but do not degrade the synthetic double-stranded RNA poly(I) . poly(C), or double or single-stranded DNA. RNAase 1 inhibits DNA synthesis and increases degradation of RNA in granulation-tissue fibroblasts but RNAase 2 at the same concentration does not have these effects.