Activation of mammalian DNA ligase by polyamines

Abstract

The activity of calf thymus DNA ligase was stimulated 2- to 3-fold by the addition of putrescine, spermidine and spermine. The optimal concentrations were 5 mM for putrescine, 0.5 mM for spermidine and 0.05–0.1 mM for spermine. Spermidine not only lowered the apparent Km value for Mg 2+ but also elevated the V value, whereas the apparent Km value for ATP was not changed. In the presence of Mn 2+ as a divalent cation, the V value was stimulated 3-fold by 0.5 mM spermidine. Monovalent cations, such as KCl and NaCl could replace the polyamines at the optimal concentrations of 50 mM and diminish the stimulation by the polyamines.