Isolation and Characterization of an Apurinic Endodeoxyribonuclease from the Anaerobic Thermophile Desulfotomaculum nigrificans

Abstract

An endodeoxyribonuclease specific to apurinic sites in DNA was purified 12000-fold from vegetative cells of the anaerobic thermophilic bacterium, Desulfotomaculum nigr$cans strain IF0 13698. The enzyme specifically hydrolyses phosphodiester bonds of apurinic doublestranded DNA, without action on normal, alkylated, or single-stranded depurinated DNA. The endodeoxyribonuclease has a molecular weight of about 18500 and a sedimentation value of 2-2s. The enzyme has an optimum pH of 7.5-8.0 and an optimum temperature of 55 "C. The half-life of purified enzyme is 55 min at 60 "C but it can be heated at 60 "C for at least 60 min without loss of activity in the presence of BSA. The purified enzyme has an absolute requirement for Mg2 + or Mn2+, and is inhibited by EDTA. Enzyme activity is completely inhibited by 0.5 M-NaCl or 1 mM-p-chloromercuribenzoate. All these properties differ from those of apurinic/apyrimidinic endodeoxyribonucleases isolated from Bacillus subtilis, Bacillus stearothermophilus, and Escherichia coli.

Apurinic and apyrimidinic DNA endonuclease of extremely thermophilic Thermothrix thiopara

“…." (17). At the same time, there are only two publications which describe AAP endonucleases from thermophilic bacteria (3,17).…”

“…(17). At the same time, there are only two publications which describe AAP endonucleases from thermophilic bacteria (3,17). The data presented in these papers do not quantitatively characterize the incision capacities of these enzymes for, AP sites.…”