JBC, Vol. 252, Issue 4, 1235-1242, Feb, 1977
Human endonuclease specific for apurinic/apyrimidinic sites in DNA. Partial purification and characterization of multiple forms from placenta
W. S. Linsley, E. E. Penhoet and S. Linn
Six chromatographically distinct forms of endonuclease active on apurinic
and apyrimidinic sites in DNA have been purified away from DNA
phosphatases, DNA N-glycosidases, and other DNases of human placenta. The
forms seem to be monomeric proteins of 27,000 to 31,000 daltons, and
although catalytically similar, they can be distinguished from one another
on the basis of substrate Km and the effects of small molecules such as
ATP. Analysis of enzymatic activity on a spectrum of damaged DNA substrates
indicates that the enzyme forms probably act at an appreciable rate only
adjacent to the phosphodiester bond of a deoxyribose lacking a base (purine
or pyrimidine) in duplex DNA; such sites can be formed by treating the DNA
with acid, alkylating agents, DNA N-glycosidases, and, probably, x-rays and
OsO4. The incision is made so as to form a deoxyribose 5'-phosphate and a
3'-hydroxynucleotide.