RT Journal Article SR Electronic(1) A1 Hunt, Robert E. A1 Cowles, Joe R.YR 1977 T1 Physiological Levels and Properties of Polynucleotide Phosphorylase of Rhizobium meliloti JF Microbiology, VO 102 IS 2 SP 403 OP 411 DO https://doi.org/10.1099/00221287-102-2-403 PB Microbiology Society, SN 1465-2080, AB Polynucleotide phosphorylase activity was demonstrated in free-living and the symbiotic bacteroid forms of Rhizobium meliloti and in free-living Rhizobium japonicum. Crude extracts of R. meliloti f-28 catalysed the polymerization of 3·0 μmol ADP (mg protein)−1 h−1. The polynucleotide phosphorylase activity of symbiotic R. meliloti was about 50 % of that of free-living R. meliloti and remained almost constant throughout the development of the nodules. Partially-purified fractions of free-living R. meliloti f-28 catalysed the polymerization of ribonucleoside diphosphates, the phosphorolysis of synthetic homopolymers and natural heteropolymers, and the β-phosphate exchange reaction. The enzyme had a pH optimum of 8·0 and had an obligatory requirement for Mg2+ for maximum activity. The phosphorylase was not highly primer-dependent, had low specificity for guanosine-containing substrates, and exhibited cooperative-type kinetics., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-102-2-403