Multiple allosteric sites are involved in the modulation of insulin‐degrading‐enzyme activity by somatostatin. (29th September 2016)

• Record Type: Journal Article
• Authors: Tundo, Grazia R.; Di Muzio, Elena; Ciaccio, Chiara; Sbardella, Diego; Di Pierro, Donato; Polticelli, Fabio; Coletta, Massimo; Marini, Stefano
• Is Part Of: FEBS journal. Volume 283:Number 20(2016)
• Page Start: 3755
• Page End: 3770
• Publication Date: 2016-09-29
• Subjects: Alzheimer's disease -- bradykinin -- insulin degrading enzyme -- somatostatin -- β‐amyloid; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.13841
• Languages: English
• ISSNs: 1742-464X

Abstract

Abstract : Somatostatin is a cyclic peptide, released in the gastrointestinal system and the central nervous system, where it is involved in the regulation of cognitive and sensory functions, motor activity and sleep. It is a substrate of insulin‐degrading enzyme (IDE), as well as a modulator of its activity and expression. In the present study, we have investigated the modulatory role of somatostatin on IDE activity at 37 °C and pH 7.3 for various substrates [i.e. insulin, β‐amyloid (Aβ)1–40 and bradykinin], aiming to quantitatively characterize the correlation between the specific features of the substrates and the regulatory mechanism. Functional data indicate that somatostatin, in addition to the catalytic site of IDE (being a substrate), is also able to bind to two additional exosites, which play different roles according to the size of the substrate and its binding mode to the IDE catalytic cleft. In particular, one exosite, which displays high affinity for somatostatin, regulates only the interaction of IDE with larger substrates (such as insulin and Aβ1–40 ) in a differing fashion according to their various modes of binding to the enzyme. A second exosite, which is involved in the regulation of enzymatic processing by IDE of all substrates investigated (including a 10–25 amino acid long amyloid‐like peptide, bradykinin and somatostatin itself, which had been studied previously), probably acts through the alteration of an 'open–closed' equilibrium. Abstract : Somatostatin is a substrate for and modulates the activity and expression of the Insulin‐Degrading Enzyme (IDE). Here, we have investigated the modulatory role of somatostatin on IDE activity for various substrates (Insulin, Aβ1–40 and Bradykinin). Somatostatin binds the IDE catalytic site and two additional exosites. It has different roles depending on the size of the substrate and its binding mode to IDE.