**5. Metallothionein redox cycle and function**

The MT redox cycle play an important role in the MT biologic function. It might link to homeostasis of the essential metals, detoxification of the toxic metals and protection against the oxidative stress. Advancement in MT research is shown by demonstrating redox regulation of the Zn-S interaction and zinc coupling. The Zn-MT cluster structure provides some chemical basis through which the cysteine ligand induces the oxido reductive properties. These structure permits for the thermo-dynamic stability of Zn in the MT. The decrease of oxidized MT can restore Zn binding ability, thereby replicates endogenous reservoir of zinc [21]. These process constitutes the redox cycle of MT, as depicted in the **Figure 2**, that provides some new perspective upon MT biologic function.

**Figure 2.** *Redox cycle of MT.*

*Metallothioneins: Diverse Protein Family to Bind Metallic Ions DOI: http://dx.doi.org/10.5772/intechopen.97658*

Under the physiologic conditions, Zn that bounds to the MT are been released from the thiolate group oxidation. The MT disulfide and/or thionin formation follows a Zn release. The MT disulfide and/or the thionin undergoes some degradation, however, when the oxidized environment gets reduced. This reduction progress is more in occurrence of a catalyst (selenium). These processes constitute the MT redox cycle, which plays a critical role in biologic function of MT.
