*Review* **Membrane-Bound Class III Peroxidases: Unexpected Enzymes with Exciting Functions**

**Sabine Lüthje 1,\* and Teresa Martinez-Cortes <sup>2</sup>**


Received: 6 August 2018; Accepted: 17 September 2018; Published: 21 September 2018

**Abstract:** Class III peroxidases are heme-containing proteins of the secretory pathway with a high redundance and versatile functions. Many soluble peroxidases have been characterized in great detail, whereas only a few studies exist on membrane-bound isoenzymes. Membrane localization of class III peroxidases has been demonstrated for tonoplast, plasma membrane and detergent resistant membrane fractions of different plant species. In silico analysis revealed transmembrane domains for about half of the class III peroxidases that are encoded by the maize (*Zea mays*) genome. Similar results have been found for other species like thale-cress (*Arabidopsis thaliana*), barrel medic (*Medicago truncatula*) and rice (*Oryza sativa*). Besides this, soluble peroxidases interact with tonoplast and plasma membranes by protein–protein interaction. The topology, spatiotemporal organization, molecular and biological functions of membrane-bound class III peroxidases are discussed. Besides a function in membrane protection and/or membrane repair, additional functions have been supported by experimental data and phylogenetics.

**Keywords:** *Arabidopsis thaliana*; Class III peroxidase; *Medicago truncatula*; microdomains; phylogenetics; plasma membrane; protein–protein interaction; *Oryza sativa*; tonoplast; *Zea mays*
