Properties of plant nuclease 1 purified from Tradescantia leaves by binding to Concanavalin A-Sepharose

Abstract

A nuclease with 3'-nucleotidase activity was purifed at least 2,500-fold from Tradescantia paludosa leaves by a process that included chromatography on Concanavalin A-Sepharose. The preparation contains several active isozymes without impurities as judged by gel electrophoresis, but immunological tests revealed one or two mJor and a few minor inactive components. Phosphatase, phosphodiesterase and 5'-nucleotidase were absent or minimal, as were the known glycoproteins, peroxidase and esterase. The nuclease was highly active on RNA and denatured DNA, and less active on native DNA; it hydrolyzed the substrates in endonuclease manner. The mononucleotides had 5'-phosphate ends. Nuclease activity was optimal at pH 5.5-6.5 in tris-acetate buffers, 0.05-0.1 M. DNase activity was insensitive to EDTA and not stimulated by Me" or Ca". Poly A and poly U were good and poly C and poly G poor substrates for the nuclease. but Id)GMP was the predominant mononucleotide from digests of nucleic acids. 3'-AMP, GMP and UMP were about equally good substrates for the nucleotidase at pH 6 but 3'-CMP was degraded at 1/5th the rate with 3'-AMP, and any activity on deoxynucleotides was very slight.