[Effect of bivalent metal ions on enzymatic activity of Ca2+, Mg2+-dependent DNAse from sea urchin Stronglyocentrotus intermedius embryos]

Abstract

Ca2+, Mg2+-dependent DNAse has been isolated in a homogeneous state from the embryos of the sea urchin Strongylocentrotus intermedius. The enzyme hydrolyzes DNA only in the presence of bivalent metal ions and is inhibited by EDTA and EGTA. The most effective activators are Mn2+ and Co2+. In the presence of Mg2+ + EGTA, Ca2+, Ba+2 and Sr2+ the DNA is hydrolyzed in a lesser degree. Mg2+ + Ca2+ as well as Mg2+ + Sr2+ produce a synergic activating effect. The concentration of Ca2+ making up to one half of the maximal activity in the presence of 5 mM MgCl2 decreases with an increase in DNA concentration from 1.10(-4) M Ca2+ for 1,7 . 10(-5) M DNA-P up to 3,0 . 10(-5) M Ca2+ for 16,0. 10(-5) M DNA-P. The value of V for enzymatic hydrolysis of DNA does not depend on the concentration of Ca2+, while Km(app) for the enzyme increases from 2,0 . 10(-5) M DNA-P for 5 . 10(-4) M Ca2+ up to 25 . 10(-5) M DNA-P for 1 . 10(-5) M Ca2+. The Km(app) of the enzyme for Mg2+ + EGTA is 3.2 . 10(-5) M DNA-P, for Ca2+--0,77 . 10(-5) DNA-P.