The effect of divalent cations on the catalytic activity of the human plasma 3'-exonuclease.
The 3'-exonuclease from human plasma is a soluble form of nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) (EC 3.1.4.1/EC 3.6.1.9). Here, the possibility of divalent cation influence for the 3'-exonuclease activity was investigated using the phosphorothioate congener of oligonucleotide containing all phosphorothioate internucleotide linkages of the [R(P)]-configuration ([R(P)-PS]-d[T(12)]) as the substrate for this enzyme. It was found that the 3'-exonuclease is a metalloenzyme, i.e. its phosphodiesterase activity was completely abolished at 0.8 mM concentration EDTA and, in turn, it was restored in the presence of Mg(2+) or Mn(2+) ions. In addition, Mg(2+) can be replaced effectively by Ca(2+), Mn(2+), or Co(2+), but not by Ni(2+) and Cd(2+) during the hydrolysis of the phosphorothioate substrate in human plasma. In addition, the mechanism is postulated, by which a single internucleotide phosphorothioate bond of the S(P)-configuration at the 3'-end of unmodified phosphodiesters (PO-oligos), or their phosporothioate analogs (PS-oligos) protects these compounds against degradation in blood.
Wojcik
Marzena
M
Department of Structural Biology, Medical University of Łódź, 7/9 Żeligowskiego St, 90-752, Lodz, Poland. marzena.wojcik@umed.lodz.pl
Stec
Wojciech J
WJ
D002384:Catalysis / Q000187:drug effects; D002413:Cations, Divalent / Q000494:pharmacology*; D004492:Edetic Acid / Q000494:pharmacology; D005092:Exonucleases / Q000097:blood* / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008956:Models, Chemical; D010710:Phosphates / Q000378:metabolism; D013873:Thionucleotides / Q000378:metabolism
D002413:Cations, Divalent; D010710:Phosphates; D013873:Thionucleotides; D008345:Manganese; D004492:Edetic Acid; D005092:Exonucleases; C022650:spleen exonuclease; D008274:Magnesium; C035638:thiophosphoric acid