On the mechanism of action of ribonucleases: dinucleotide cleavage catalyzed by imidazole and Zn2+.
Cyclization/cleavage of the 2-(p-nitrophenyl) phosphate ester of propylene glycol is catalyzed by imidazole and, much more effectively, by Zn2+ with imidazole. In the latter case, the mechanism involves simultaneous Lewis acid/base catalysis. Similar Zn2+ and imidazole catalysis of cyclization/cleavage is seen with the dinucleotide 3',5'-UpU (uridylyluridine). Again, the zinc system is much more effective than is catalysis by imidazole alone, and in this case simultaneous Lewis acid/base catalysis substitutes for the sequential proton acid/base catalysis seen with polynucleotides or dinucleotides and imidazole buffer catalysts. A mechanism is proposed for catalysis of RNA cleavage by the enzyme ribonuclease A, and the relationship of that mechanism to the action of the enzyme model systems is discussed.
Breslow
R
R
Department of Chemistry, Columbia University, New York, NY 10027.
Huang
D L
DL
Anslyn
E
E
D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D007093:Imidazoles / Q000378:metabolism*; D007700:Kinetics; D009841:Oligonucleotides / Q000378:metabolism*; D011072:Poly U / Q000378:metabolism; D019946:Propylene Glycol; D011409:Propylene Glycols / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D012259:Ribonuclease, Pancreatic / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism*; D013816:Thermodynamics; D014529:Uridine; D015032:Zinc / Q000378:metabolism*
D007093:Imidazoles; D009841:Oligonucleotides; D011409:Propylene Glycols; D011072:Poly U; D012313:RNA; D019946:Propylene Glycol; C029899:imidazole; D012260:Ribonucleases; D012259:Ribonuclease, Pancreatic; D015032:Zinc; D014529:Uridine