A Study of the Native-Denatured (N⇌D) Transition in Lysozyme

Abstract

Kinetic analyses of the protease digestion of several chemical derivatives of lysozyme [EC 3.2.1.17] showed that only the D(denatured) state of the protein is digested and that the reaction velocity is proportional to the equilibrium constant (K_D) of the N⇌D transition of the protein. Alteration of the net charge of lysozyme by acetylation caused a shift of the N⇌D transition to the right (ten-fold increase in K_D compared to that of native enzyme). Both the formation of a lysozyme-inhibitor complex and the introduction of a covalent bond in the lysozyme molecule restricted the transition. The magnitude of the N⇌D transition is related to the susceptibility of lysozyme to protease digestion and it is estimated that the N⇌D transition in proteins is generally important in the intracellular catabolism of proteins.