| Abstract: | The ATP-dependent exonuclease V from Micrococcus lysodekticus shows a Michaelian relation between steady-state velocity and the concentration of T7 DNA substrate. The Km (expressed as a mass concentration) does not change when the T7 DNA is broken into smaller fragments by a restriction enzyme. This is interpreted to mean that the predominant process by which the exonuclease-V--DNA complex breaks down is digestion of the entire DNA molecule rather than physical dissociation, in accord with the already known processive nature of degradation by this enzyme. The way that the V and Km towards DNA vary with ATP and ADP concentration suggests that enzyme-DNA complex is predominantly formed by reaction of DNA with an enzyme-ATP complex rather than with bare enzyme. |
