Introduction A Chemical Reactions Catalyzed

Ribonucleases depolymerize ribonucleic acids by cleavage of phosphoric diester bonds between nucleotide residues. This means that they are specialized phosphotransferases or phosphoric diester hydrolases. A further specification is that they are endonucleases, as exonucleases degrade nucleic acids from one of the two termini, which results in little depolymerization. Cleavage may occur between phosphate and the 3'-oxygen of the ribose, producing 5 '-phosphomonoesters (EC 3.1.26) or between phosphate and the 5'-oxygen of the ribose, producing 3 '-phosphomonoesters (EC 3.1.27). Enzymes with the latter cleavage specificity often are transferases producing 20,3 0-cyclic phosphate as intermediates, which generally are hydrolyzed in a second reaction catalyzed by the same enzyme. Figure 1 shows as an example the two successive reactions catalyzed by bovine pancreatic ribonuclease.

0 0

Post a comment