The eight human “canonical” ribonucleases: Molecular diversity, catalytic properties, and special biological actions of the enzyme proteins

Abstract 

Human ribonucleases (RNases) are members of a large superfamily of rapidly evolving homologous proteins. Upon completion of the human genome, eight catalytically active RNases (numbered 1–8) were identified. These structurally distinct RNases, characterized by their various catalytic differences on different RNA substrates, constitute a gene family that appears to be the sole vertebrate-specific enzyme family. Apart from digestion of dietary RNA, a wide variety of biological actions, including neurotoxicity, angiogenesis, immunosuppressivity, and anti-pathogen activity, have been recently reported for almost all members of the family. Recent evolutionary studies suggest that RNases started off in vertebrates as host defence or angiogenic proteins.

Abbreviations: RNase(s), ribonuclease(s), RI, ribonuclease inhibitor protein, EDN, eosinophil-derived neurotoxin, ECP, eosinophil cationic protein, ang, angiogenin, ORF, open reading frame, dsRNA, double-stranded RNA

Keywords: Human RNase, Vertebrate RNase superfamily, Eosinophil neurotoxin, Human angiogenin, Host-defence protein