Enzymatic Photoreactivation of DNA

摘要

The distinguishing hallmarks of photoreactivation of DNA is the enzyme-mediated, light-dependent monomerization of pyrimidine dimers resulting in repair of the DNA and restoration of its biological integrity. Photoreactivation is differentiated from sensitized dimer monomerization by small molecules by the participation of the protein macromolecule and from dimer monomerization by tryptophan-containing peptides and proteins by their wavelength dependence. The photoreactivating enzyme shows three levels of specificity: first, for the length and kinds of nucleic acid; second, for cis-syn cyclobutyl pyrimidine dimers; and third, for photoreactivating photons of wavelength 300 to 600 nm. Although all photoreactivating enzymes characterized to date show this specificity in function, current reports indicate possible heterogeniety in structure. Most PR enzymes (E. coli, T. domestica (silverfish), H. sapiens, S. griseus) are composed of a single polypeptide chain with a molecular weight of 35,000 to 40,000 d. However, the yeast enzyme is reported to be composed of two dissimilar subunits with molecular weights 60,000 and 85,000. (ERA citation 03:038137)