[Inactivation and reactivation of proteins (enzymes)]

Numerous examples of protein inactivation are considered. Several principal inactivation mechanisms are distinguished: aggregation, thiol-disulfide exchange, alteration in the protein primary structure, dissociation of cofactor molecules from the enzyme active site, dissociation of proteins with quaternary structure into subunits, and conformational changes. All the mechanisms interweave during protein inactivation. In many cases, however, conformational transformations in protein play an important role; they accompany and often trigger other mechanisms of inactivation which would be impossible without preliminary alterations in protein structure. The published data on reactivation of inactivated proteins are considered. Reactivation was a success when inactivation was caused by aggregation, chemical modification of SH-groups of S-S bonds, or resulted from "irreversible" conformational changes.