The active site and mechanism of action of bovine pancreatic ribonuclease. 7. The catalytic mechanism

Abstract
An hypothesis for the active site and mechanism of action of ribonuclease is presented. In the hydrolysis of cytidine 2[image],3[image]-phosphate a histidine in the acid form transfers a proton to the 2[image]-oxygen atom of the nucleotide and a proton from water (or an alcohol) is transferred to another histidine. In the cyclization of an ester of cytidine 3[image]-phosphate, such as ribo-nucleic acid, the function of these two histidines is reversed.