Aluminum modulation of proteolytic activities

Abstract

The effect of aluminum ions on the activity of proteolyic activities, mainly serine proteases and calpains, has been examined. Aluminum affects the biological activity of proteolytic activities either through a direct effect on the enzyme molecule or through a deregulation of the control mechanisms acting on them. Binding of the ion, most likely results in molecular rearrangements affecting both the substrates binding site and the site involved in the recognition of macromolecular inhibitors. As whole, the data reported clearly indicate that aluminum significatively affects the intracellular protein turnover, most likely triggering catastrophic events for the cellular life. The physiopathological significance of these effects has been discussed, in particular for neurological disorders (the Alzheimer's disease included) where an imbalance of proteolytic as well as antiproteolytic systems appears a crucial event both for the formation of neuritic plaques and neurofibrillary tangles which are the major hallmarks of the disease. #

Metal ions affect insulin-degrading enzyme activity

“…4. The principal fragments (see Table 1) are B20-25 (m/z: 754.3) and B26-30 (m/z: 725.4), indicating that two of the principal insulin cleavage sites (namely B (25)(26) and B (24)(25)) are specific cleavage sites for the interaction between IDE and insulin [13]. Other less specific peptide fragments also appear in the spectrum for a very long incubation time (Fig.…”

“…We carried out enzymatic digestions of B20-30, in the presence or absence of copper(II), aluminum(III) and zinc(II), metals chosen for their important role in neurodegenerative diseases [24,26,66,67]. Moreover, since copper enters the cell as copper(I) through high-affinity plasma membrane copper transporters or low affinity permeases [68] and IDE is mainly cytosolic [1], it is interesting to analyze the effect of both oxidation states on B (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) processing. Furthermore, as silver belongs to the same group of copper and silver(I) has the same chemistry of copper(I), we have also performed studies using this ion, in order to have a replication of the copper(I) results without any possible invalidation due to copper(I) oxidation problems (although we worked in a reducing environment, copper(I) could be oxidized to copper(II) during the incubation with the enzyme).…”

“…To assess how metal ions affect the IDE enzymatic activity, steady state kinetics on the B (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) peptide in the presence and in the absence of the above mentioned ions were performed. Fig.…”

“…It is also interesting to outline that if we compare these parameters with those obtained for the amyloid peptides Aβ [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and Aβ [16][17][18][19][20][21][22][23][24][25][26][27][28] several similarities and some differences emerge [54]. In particular, the overall proteolytic activity toward the main cleavage sites (i.e., Phe 24 [16][17][18][19][20][21][22][23][24][25][26][27][28] ) is somewhat higher in the case of the B20-30 peptide due to a slightly more efficient cleavage rate-limiting step (see Table 2), whereas the substrate affinity of B20-30 appears intermediate between that of Aβ [1][2][3]…”

“…In this scenario, as metal ions are essential for many metabolic processes and their homeostasis is crucial for life [24][25][26], the elucidation of their roles on the modulation of IDE activity represents an important issue that could give an insight on the biomolecular mechanisms involved with the above mentioned diseases. Recently, zinc [27] and copper [28] have been identified to have a crucial role on insulin action and, ultimately, in diseases such as DM2.…”