Stability of alkali phosphatase from E-coli

A mechanism of variations in the activity of oligomeric enzymes caused by t he decomposition of interprotein contacts to protomers was considered by th e example of alkali phosphatase(AP) extracted from E. coli. The kinetic cur ves for the thermal inactivation of AP obtained under various conditions ex hibited induction periods, which were attributed to structural changes in t he conformational lock of the AP dimer. It was found that the stable AP dim er becomes labile and capable of dissociating after the destruction of two of the three contacts of its conformational lock. Destabilizers (2.5 M urea and 0.02 M MgSO4) favored the destruction of the conformational lock and c aused an increase in the rate constant for the decomposition of labile dime rs, but had no effect on the rate constant for the denaturation of protomer s.