Cytidine, 3 ,5 -cyclic phosphate, hydrolysis

With cytidine cyclic phosphate as a substrate the step 2 process alone is measured. The procedure of Crook et al. (395) relies on the increase in absorbance at 286 nm which occurs on hydrolysis of the cyclic phosphate ring. Cleavage of the ring also results in proton release which is the basis of the titrimetric procedure described by Stark and Stein (132). The assays employing C>p are usually carried out in 0.35 M NaCl. The ionic strength for maximum activity is much higher for this substrate than for RNA. A brief summary of the above procedures is given by Klee (396). 

Eftink, M. R. and Biltonen, R. L. (1983) Energetics of Ribonuclease A Catalysis. 1. pH, Ionic Strength, and Solvent Isotope Dependence of the Hydrolysis of Cytidine Cyclic 2, 3 Phosphate, Biochemistry 22,... 

Adenylic acids o and b were each converted by trifluoroacetic anhydride into the same 2 3 -cyclic phosphate (13, R = adenin-9-yl) by Brown, Magrath, and Todd. These authors also applied this method to the synthesis of 2 3 -cyclic phosphates (13) of cytidine, uridine, and guanosine. Hydrolysis of these cyclic phosphates gave the corresponding a and b nucleotide mixtures. Markham and Smith found that, during hydrolysis of ribonucleic acid with pancreatic ribonuclease, the 2 3 -cyclic phosphates of the pyrimidine nucleosides are formed as intermediates leading to the ribonucleoside phosphates b. The also showed that 2 3 -cyclic phosphates (13) are formed by very mild, alkaline hydrolysis of ribonucleic acid. The discoveries of these a and b isomers of mononucleotides from... 

If this hypothesis is correct, it is surprising that, in the acid hydrolysis of (175) and of cytidine 3 5 -cyclic phosphate, the presence of nucleotides of type (177) or (181), or both, was not observed. Neither was the presence of D-xylose or n-arabinose noted in the hydrolyzates. It may... 

This compound has been isolated after subjecting yeast ribonucleic acid to brief acid hydrolysis. When it is treated with alkali there is cleavage at (1), with the formation and subsequent hydrolysis of a cyclic anhydride of guanylic acid. The final products are guanosine-2 -phosphate, guanosine-3 -phosphate, and cytidine-3 -phosphate. The last two would be split by 3-nucleotidase from barley. 

The possibility that, during the alkaline hydrolysis of ribonucleic acid, tri-esters (18) - could be intermediates was ruled out on mechanistic groxmds."f > Furthermore, it was shown that the tri-ester, uridine 2 3 -(methyl phosphate) (18, R = CH3), synthesized by methylation of uridine 2 3 -cychc phosphate with diazomethane, is resistant to ribo-nuclease. f However, it has been observed that, when the benzyl ester of cytidylic acid 6 is partially hydrolyzed in acid, a significant proportion of the o isomer of this phosphoric diester is formed." ) In addition, the dinucleoside phosphates, such as adenylyl-(3 —>5 )-cytidine (14a), are also isomerized to the corresponding (2 - 5 )-dinucleoside phosphates by treatment with acid. " These studies suggest that cyclic triesters (or derivatives thereof) may be intermediates in isomerization of these phospho-diesters in acidic mediiun. 

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