Releases hydrogen peroxide in the apoplast which may be important for cross-linking reactions in the cell wall biochemistry. May play an important role in several aspects of plant growth and defense mechanisms. 2 H(+) + O2 + oxalate = 2 CO2 + H2O2 Homo hexamer; a trimer of dimers. By salt stress. Glycosylated. A form called G contains antennary GlcNAc residues, whereas a form called G' lacks antennary GlcNAc residues in its otherwise identical glycans. Belongs to the germin family.