Association and dissociation of the tripeptidyl-peptidase II complex as a way of regulating the enzyme activity.

Tripeptidyl-peptidase II is an unusually large exopeptidase. The subunits (M(r) = 138,000) form an active complex with an M(r) > 10(6). This paper demonstrates that the complex can spontaneously dissociate in vitro into dimers which retain 110th of the original specific activity. The dissociated enzyme can reassociate at elevated temperatures, provided the protein concentration is sufficiently high. This reassociation was accompanied by a reactivation. The rate of reactivation was increased by the presence of competitive peptide inhibitors. It is speculated that association/dissociation may be a way of regulating the enzyme activity in vivo. Copyright 2000 Academic Press.