[134] Polynucleotide phosphorylase from Escherichia coli

Physiological Levels and Properties of Polynucleotide Phosphorylase of Rhizobium meliloti

“…In addition, the phosphorolysis activity of crude extracts of R . meliloti [I '85 units (mg protein)-l] was three times greater than that reported in crude extracts of E. coli (Kimhi & Littauer, 1968).…”

“…A second difference was the relative ineffectiveness of GDP and poly(G) as substrates for the R. meliloti phosphorylase system. In E. coli, for example, the rates of diphosphate-P, exchange for ADP and GDP were similar (Kimhi & Littauer, 1968). Methods used in other systems to stimulate GDP polymerization (Fresco & Su, 1962), e.g.…”

Phosphorolysis of Aminoacyl‐tRNA by Polynucleotide Phosphorylase from Escherichia coli

“…It seemed that the valine derivative which had arisen from the phosphorolysis of valyl-tRNA was Pi, overall phosphorolysis of tRNA was followed by incorporation of [s2P]Pi into nucleoside diphosphates as previously described [9]. The specific radioactivity of the phosphate was 4 x lo5 counts x min-l x pmole-1…”

“…The specific activity of the enzyme was 105units/mg. The definition of an enzyme unit and assay methods have been described previously [9]. E .…”

“…The purified tRNAVa1 thus obtained accepted 1.33 nmoles of valine per A,,, unit (measured in 0.5 M NaC1, 0.01 M MgSO,). Purified polynucleotide phosphorylase was prepared according to Kimhi and Littauer [9]. The specific activity of the enzyme was 105units/mg.…”