Kinetics and thermodynamic study on the chemical reduction of macroimmunoglobulins.

The chemical reduction of human macroglobulin from its native pentameric form to reduced monomers has been followed using three different methods. The following parameters were measured under different conditions of pH, T and concentration: time dependent kinetics of the turbidity effect at 320 nm, chemical titration of -SH groups, and the determination of the heat effects evolved with time. The results obtained showed the same kinetics parameters for the reaction and indicate that the reduction of the 26 S-S bridges proceeds cooperatively from the pentameric structure to the monomeric one without the formation of intermediate states. The enthalpic contribution measured calorimetrically suggests that a conformational change of the chains structure occurs during the reduction.