Domain of unknown function (DUF1929). Members of this family adopt a secondary structure consisting of a bundle of seven, mostly antiparallel, beta-strands surrounding a hydrophobic core. The 7 strands are arranged in 2 sheets, in a Greek-key topology. Their precise function, has not, as yet, been defined, though they are mostly found in sugar-utilising enzymes, such as galactose oxidase.

C-terminal Early set domain associated with the catalytic domain of galactose oxidase. E or "early" set domains are associated with the catalytic domain of galactose oxidase at the C-terminal end. Galactose oxidase is an extracellular monomeric enzyme which catalyzes the stereospecific oxidation of a broad range of primary alcohol substrates and possesses a unique mononuclear copper site essential for catalyzing a two-electron transfer reaction during the oxidation of primary alcohols to corresponding aldehydes. The second redox active center necessary for the reaction was found to be situated at a tyrosine residue. The C-terminal domain of galactose oxidase may be related to the immunoglobulin and/or fibronectin type III superfamilies. These domains are associated with different types of catalytic domains at either the N-terminal or C-terminal end and may be involved in homodimeric/tetrameric/dodecameric interactions. Members of this family include members of the alpha amylase family, sialidase, galactose oxidase, cellulase, cellulose, hyaluronate lyase, chitobiase, and chitinase, among others.

Glyoxal oxidase N-terminus. This family represents the N-terminus (approximately 300 residues) of a number of plant and fungal glyoxal oxidase enzymes. Glyoxal oxidase catalyzes the oxidation of aldehydes to carboxylic acids, coupled with reduction of dioxygen to hydrogen peroxide. It is an essential component of the extracellular lignin degradation pathways of the wood-rot fungus Phanerochaete chrysosporium.