biologia plantarum

Biologia plantarum 22:143-151, 1980 | DOI: 10.1007/BF02878255

Nucleases in chloroplast of barley

Jiřina Švachulová¹, J. Velemínský¹, J. Šatava¹

¹ Institute of Experimental Botany, Czechoslovak Academy of Sciences, Praha 6, Czechoslovakia

Two barley chloroplast nuclease fractions were separated by the affinity chromatography and gel electrophoresis. Both were about 2 times more active to RNA than to native DNA and about half as active to denaturated DNA as to native DNA. Both fractions were as active to UV-irradiated (270 J m^-2) native DNA as to intact DNA but their action was inhibited by apurinic sites. The enzyme activities were inhibited by high concentrations of EDTA, NaCl, Mn²⁺, Ca²⁺, Zn²⁺ ions and by N-ethylmaleimide. They do not require Mg²⁺ ions but are stimulated or at higher concentration inhibited by their presence. Both RNase and DNase were active over a wide pH range (5.5-9), the optimum for DNase action in the presence of Mg²⁺ being 6.5, for RNA decomposing activity at pH 8.0. As no mononucleotides were detected in acid soluble form, it seems likely that DNase acts in the endonucleolytic way.

Received: October 1, 1979; Accepted: October 25, 1979; Published: March 1, 1980  Show citation