Depurination

Depurination

In molecular genetics, depurination is an alteration of DNA in which the purine base (adenine or guanine) is removed from the deoxyribose sugar by hydrolysis of the beta-N-glycosidic link between them. After depurination, an apurinic site is formed where the sugar phosphate backbone remains and the sugar ring has a hydroxyl (-OH) group in the place of the purine. Studies estimate that as many as 5,000 purines are lost this way each day in a typical human cell. One of the main causes of depurination is the presence of endogenous metabolites in cell undergoing chemical reactions. Depurinated bases in double-stranded DNA are efficiently repaired by portions of the base excision repair (BER) pathway. Depurinated bases in single-stranded DNA undergoing replication can lead to mutations, because in the absence of information from the complementary strand, BER can add an incorrect base at the apurinic site, resulting in either a transition or transversion mutation. Loss of pyrimidine bases (Cytosine and Thymine) occurs by a similar mechanism, but at a substantially lower rate.

Read more about Depurination.