Denovo synthesis of 3'-ribonucleotidase in germinating rice embryos

The development of 3'-ribonucleotidase (EC 3.1.3.6) was completely suppressed by cycloheximide while it was not affected by actinomycin D. The specific activity of the enzyme and the radioactivity on the enzyme protein progressively increased during the purification of 3'-ribonucleotidase. On purification on Bio-Gel A-5m and polyacrylamide gel electrophoresis at pH 8.9, most of the radioactivity was found associated with the enzyme protein. This radioactivity was due to the labelling of the enzyme protein alone, as re-electrophoresis of the protein, eluted from this band, at pH4.3 showed only a single band containing all the radioactivity. All the 35S-label present on the enzyme protein was associated with methionine and cysteine in the ratio 1:2; thereby suggesting the possibility of these amino acids being present in the same molar ratio in the enzyme protein. (author)