Theoretical Study on the Hydrolytic Deamination Reaction Mechanism of Cytosine

The hydrolytic deamination reaction mechanism of cytosine(C) has been theoretically investigated at the B3LYP/6-31G** level.It is found that the hydrolytic deamination reaction of C may proceed in a stepwise way,in which a tetracoordinated intermediate is formed firstly by the hydrolysis reaction,followed by the deamination reaction with C—N broken and C=O formed.The study on the potential energy surface showed that NH3 molecule as a shuttle facilitates H transfer between keto form and enol form of hypoxanthine.However,the deamination reaction of C does not take place because of a higher barrier for the opening system,which is agreement with the experimental result.