Physical and kinetic properties of the site specific endonuclease Bam HI from Bacillus amylolique-faciens.

The site specific endonuclease Bam HI which is composed of subunits of a molecular weight of 22 000 [1] can aggregate to complexes of a molecular weight of 360 000. It is an acidic protein with an isoelectric point at pH 5.3. Optimal activity is reached at 13 mM MgCl2. A very simple method is presented to determine kinetic constants of restriction enzymes directly from agarose gel photographs without any further equipment applying the integrated Michaelis Menten equation. With pJC 80 DNA as a substrate KM was found to be 3.6 10(-10) M. The method can be used to redefine the unit activity of site specific endonucleases unambigously.