Peptides as unique tools to modulate redox levels: towards applications in living cells and in vivo

Owing to their size, their physico-chemical properties, their recognition properties and the presence of multiple coordination groups, peptides offer unique opportunities to develop peptidyl metal complexes useful for biological applications. Indeed, peptides have been widely used to produce models of metalloenzymes as their chemical versatility enables introducing modifications in a very well controlled manner to study specific properties. More recently, peptides have been studied for their antioxidant properties for nutritional, cosmetics or pharmaceutical applications. Antioxidant properties of peptides can be of different origins. Peptide can scavenge free radicals, inhibit lipid peroxidation, inhibit oxidative enzyme activity or modulate antioxidant expression. In this review, we will focus on their useful role as metal ligands highlighting the chelation of redox active endogenous metals such as Cu(I) and Fe(II) that catalysis the Fenton reaction responsible for redox homeostasis disruption. In addition, we will report on the development of peptidyl metal complexes mimicking antioxidant metalloenzymes while overcoming challenges bound to peptide by introducing sequences modifications. We will emphasize the biological applications related to these two strategies involving peptides.