Ribonucleases. Members include pancreatic RNAase A and angiogenins. Structure is an alpha+beta fold -- long curved beta sheet and three helices.
Pancreatic ribonucleases (RNaseA) are pyrimidine-specific endonucleases found in high quantity in the pancreas of certain mammals and of some reptiles [PUBMED:3940901]. Specifically, the enzymes are involved in endonucleolytic cleavage of 3'-phosphomononucleotides and 3'-phosphooligonucleotides ending in C-P or U-P with 2',3'-cyclic phosphate intermediates. Ribonuclease can unwind the DNA helix by complexing with single-stranded DNA; the complex arises by an extended multi-site cation-anion interaction between lysine and arginine residues of the enzyme and phosphate groups of the nucleotides. Other proteins belonging to the pancreatic RNAse family include: bovine seminal vesicle and brain ribonucleases; kidney non-secretory ribonucleases [PUBMED:2734298]; liver-type ribonucleases [PUBMED:2611266]; angiogenin, which induces vascularisation of normal and malignant tissues; eosinophil cationic protein [PUBMED:2473157], a cytotoxin and helminthotoxin with ribonuclease activity; and frog liver ribonuclease and frog sialic acid-binding lectin. The sequence of pancreatic RNases contains four conserved disulphide bonds and three amino acid residues involved in the catalytic activity.