*4.4. Structural Analysis*

*At*GOX1, *At*GOX2 and*Zm*GO1 3D-structures were designed based on the spinach GOX (UniProtKB: P05414) 3D-structure (PDB: 1al7.1) using the SWISS-MODEL server (https://swissmodel.expasy.org/) modelling service. Manipulation of 3D-structures was realized using Deepview (Swiss Pdb-viewer) (https://spdbv.vital-it.ch/) and included the compute H-bond formation and mutation tools.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2223-7747/9/1/27/s1, Figure S1: *At*GOX1, *At*GOX2, *At*GOX3, *At*HAOX1 and *At*HAOX2 protein sequence alignments showing the conservation of phosphorylated residues and other important residues and structures, Figure S2: Amino acid sequence alignments of *Lactococcus lactis*, *Aerococcus viridians*, *Nostoc* and *Chlamydomonas reinhardtii* lactate oxidases, with glycolate oxidases and hydroxy-acid oxidases of human and plants, Figure S3: Purified recombinant His-tag proteins of wild-type *At*GOX1, *At*GOX2 and *Zm*GO1 and their phospho-site mutated forms on Coomassie-stained SDS-PAGE gels, Table S1: Primers for site-directed mutagenesis and DNA sequencing.

**Author Contributions:** Conceptualization, M.H. and M.J.; Methodology, M.H. and M.J.; Formal Analysis, M.H. and M.J.; Investigation, M.J., Y.L. and S.M.; Resources, M.H.; Data Curation, M.H. and M.J.; Writing & Editing, M.H. and M.J.; Supervision, M.H. and M.J.; Project Administration, M.H.; Funding Acquisition, M.H. and M.J. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by a public grant overseen by the French National Research Agency (ANR) as part of the «Investissement d'Avenir» program, through the "Lidex-3P" project and a French State grant (ANR-10-LABX-0040-SPS) funded by the IDEX Paris-Saclay, ANR-11-IDEX-0003-02. This work was also supported by the ANR-14-CE19-0015 grant REGUL3P awarded to M.H., Y.L. was supported by a PhD fellowship from the China Scholarship Council.

**Acknowledgments:** We would like to thank Younès Dellero (INRA Rennes, France) who helped to initiate recombinant GOX studies in the team.

**Conflicts of Interest:** The authors declare no conflict of interest.
