A di-Copper Peptidyl Complex Mimics the Activity of Catalase, a Key Antioxidant Metalloenzyme

Abstract

Catalases (CAT) are antioxidant metalloenzymes necessary for life in oxygen-metabolizing cells to regulate H 2 O 2 concentration by accelerating its dismutation. Many physio-pathological situations are associated with oxidative stress resulting from H 2 O 2 overproduction during which antioxidant defenses are overwhelmed. We have used a combinatorial approach associated with an activity-based screening to discover a first peptidyl di copper complex mimicking CAT. The complex was studied in detail and characterized for its CAT activity both in solution and in cells using different analytical methods. The complex exhibited CAT activity in solution and, more interestingly, on HyPer HeLa cells which possess a genetically encoded ratiometric fluorescent sensors of H 2 O 2 . These results highlight the efficiency of a combinatorial approach for the discovery of peptidyl complexes that exhibit catalytic activity.affording the two electrons exchange required for the dismutation reaction. 20,22,23 Small molecular complexes mimicking CAT have been developed to reduce oxidative stress in pathological conditions. [28][29][30] These bioinspired mimics are thus mainly mononuclear (Mn or Fe) porphyrin derivatives or dinuclear manganese complexes analogous to the active site of HemeCAT or MnCAT, respectively. 29 Dinuclear Mn complexes bioinspired from MnCAT are alkoxo, phenoxo, or oxo/carboxylato bridged complexes. In an excellent review, Signorella and Hureau have reported that besides the redox potentials of the metal ions key to catalytic H 2 O 2 dismutation, the efficacy of the complexes is associated with the presence of an intramolecular base to assist in deprotonation. In addition, the presence of a vacant site on the Mn ion is required to coordinate H 2 O 2 , but the complex stability is reduced by the protonation of the bridging ligand. 31 Few mononuclear copper complexes 30,[32][33][34][35][36] have been reported as CAT mimics as well but examples of dinculear copper complexes are very rare. [37][38][39][40] Generally, CAT mimics have been studied in organic solvents or have exhibited activity only at pH above 8. So far, contrarily to SOD mimics, no peptidyl complexes mimicking CAT have been reported, whatever the metal ion. [41][42][43][44] This may be explained by the difficulty to rationally design short peptides able to bind two metal cations (to afford the two required electrons) with appropriate redox potentials and affinities. However, peptidyl ligands are of great interest since their synthesis is very versatile, they are biocompatible and water soluble. But it seems highly complicated to design Mn-based peptidyl complexes since peptide affinity for Mn(II) is usually in the 10 3 -10 6 range at physiological pH even for quite long sequences. [45][46][47] In contrast, short peptide sequences have been described to bind Cu(II) with high affinities (ca. 10 12 -10 15 ). 42,48,49 In this manuscript, we describe implementation of a combinatorial approach to synthesize a library of copper complexes, associated with an ...

Improvement of Peptidyl Copper Complexes Mimicking Catalase: A Subtle Balance between Thermodynamic Stability and Resistance towards H2O2 Degradation

“…The screening of a combinatorial library of peptidyl copper(II) complexes combined with a catalase activity-based assay enabled the identification of the first peptidyl di-copper complex with promising CAT activity [ 19 ]. This first peptide, called CATm1, is shown in Table 1 .…”

“…In such situations, its catalase-like activity will be low. The four new complexes displayed catalase-like activity, and, very interestingly, some of them showed improved features, such as higher resistance to H 2 O 2 degradation and greater thermodynamic stability in comparison with the previously described peptidyl copper complex [ 19 ].…”

“…Therefore, the development of CAT mimics that could complement CAT when these enzymes are overwhelmed may contribute to oxidative stress management. While SOD mimics have been extensively studied as potential catalytic therapeutic molecules [ 13 , 14 , 15 , 16 ], the exploration of CAT mimics is still in its infancy [ 17 , 18 , 19 ]. On the one hand, some mononuclear manganese mimics have been tested in cellular models, but they lacked stability in such intricate environments [ 17 ].…”

“…On the other hand, iron or manganese porphyrins, which are much more stable, have shown beneficial effects on H 2 O 2 -mediated loss of viability in catalase/peroxidase-deficient E. coli strains [ 18 ]. Finally, a di-copper peptidyl catalase mimic has shown the ability to reduce H 2 O 2 concentration in HeLa Hyper cells [ 19 ]. There are two types of catalases: a (monometallic) heme CAT [ 20 ] and a dinuclear manganese CAT [ 21 ], present in bacteria such as Lactobacillus plantarum [ 22 ].…”

“…However, their catalytic activity was often reported in organic solvents or at non-physiological pH because of their low solubility in aqueous pH 7.5 conditions or the need for an external base. We recently described the first peptidyl di-copper complex with catalase-like activity that was promising in aqueous buffer and in cells [ 19 ]. However, its first-order rate for H 2 O 2 dismutation, k cat , was still two orders of magnitude smaller than that of most active reported non-peptidyl mimics [ 18 ].…”