Final answer:
DNA glycosylases are crucial for base excision repair by recognizing and removing damaged bases from DNA. They do not cleave DNA directly but remove the damaged base by hydrolyzing the glycosidic bond, creating an abasic site for further repair by other enzymes, a process discovered by Thomas Lindahl.
Step-by-step explanation:
Do DNA glycosylases recognize and cleave glycosyl bonds in DNA?
DNA glycosylases are key enzymes that begin the process of base excision repair (BER) by recognizing and removing damaged bases in DNA. They catalyze the hydrolysis of the glycosidic bond between the base and the sugar phosphate backbone, creating an abasic site (apurinic/apyrimidinic site). After a DNA glycosylase removes an offending base, an AP endonuclease recognizes the deoxyribose with the missing base. It nicks the DNA at that nucleotide, and subsequent steps are taken by other enzymes to complete the repair process. This includes phosphodiesterase, which hydrolyzes the phosphoester bond of the 'base-less' sugar phosphate, removing it from the DNA strand. DNA polymerase then adds the correct nucleotide to the 3' end of the nick, and DNA ligase III seals the remaining nick in the strand.
The entire BER mechanism is critical for maintaining genomic stability by correcting potentially mutagenic or cytotoxic DNA lesions, such as oxidation, alkylation, or deamination changes in the DNA bases. Thomas Lindahl, a key researcher in this field, discovered many of these enzymes involved in DNA repair mechanisms.
The specificity of DNA glycosylases for different types of damages is a crucial aspect of DNA repair. For instance, treatment of DNA with various agents can reveal how certain bases are selectively targeted for excision by these enzymes. This targeting is essential for the fidelity of the repair process.