Regulation of the catalytic activity and oligomeric composition of enzymes in reversed micelles of surfactants in organic solvents

Abstract

The Phenomenon of the regulation of the catalytic activity of enzymes via changing their oligomeric composition in the system of reversed micelles of sodium bis(2-ethylhexy)sulfosuccinate (AOT) in octane was studied using z-chymotrypsin (CT) from bovine brain and alkaline phosphatase (AP) from calf intestinal mucosa. The dependences of the enzyme catalytic activity on the AOT hydration degree (W=[H2O][AOT]), the parameter determining the radius (r4) of the inner cavity of micelles, usually represent the bell-shaped curves. The maximal catalytic activity is observed at such Wo when r4 is equal to the size of the enzyme molecule. The position of this maximum strictly correlates with the enzyme oligomeric composition. Thus, in the case of CT this is observed at Wo=12 when r1 is equal to the radius (rp) of the CT globule. In the case of artificially produced conjugate containing six cross-linked CT molecules, this is observed at Wo=43 when r4 is equal to the radius of the sphere surrounding the absolute octahedron composed of six CT globules. The dependence of the catalytic activity of AP on Wo represent a curve with two maxima that are observed when r4 is equal to rp of either AP monomer (W=17) or AP dimer (Wo=25), Ultracentrifugation experiments revealed that variation of Wo causes a change in the oligomeric composition of AP its transition from monomeric (Wo<20) to demeric form (Wo > 20). Hence, the observed maxima correspond to functioning of different oligomeric forms of AP. © 1991.