Involvement of active site in self-association of proteins: a case of alpha-chymotrypsin.

The self-association of proteolytic enzymes can be looked upon as an interesting possibility of the manifestation of enzyme-substrate complex. Hence the involvement of active site in such processes is a centre of investigation for many years. In the case of alpha-chymotrypsin, considerable controversy exists with regard to the involvement of active site of the enzyme in its self-association. A historical perspective of the problem and an overview of the available evidence, for and against, is presented and critically analysed. Despite contradicting observations, accumulated evidence indicates that His-57 and Ser-195 at the active site are involved, at least partially, in the self-association; a few other groups such as Tyr-146 and Met-192 are also involved in such processes.