ION-DEPENDENT ACTIVATION AND INHIBITION OF RIBONUCLEOTIDE REDUCTASE FROM LACTOBACILLUS LEICHMANNII

The activity of ribonucleotide reductase from Lactobacillus leichmannii is affected markedly by ions. These effects can be either stimulatory or inhibitory, depending upon the nature of the dithiol substrate. When dithioerythritol is the reductant, the enzyme is activated by a variety of anions, particularly fluoride, phosphate and acetate. The largest effect (approximately 17-fold) is obtained in the presence of 1.0 M fluoride. In contrast, anions are generally inhibitory when dihydrolipoic acid serves as the reductant. These results are considered in terms of the chaotropic (structure-disrupting) and anti-chaotropic (structure-forming) effects of anions on the conformation of the enzyme, particularly at the dithiol binding site. © 1969.