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 catalysing a two-electron transfer reaction during the oxidation of primary alcohols to corresponding aldehydes. The second redox active centre 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 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 [1]. This domain is found in sugar-utilising enzymes, such as galactose oxidase or chitinase [2-6].

1: Crystal structure of the precursor of galactose oxidase: an unusual self-processing enzyme. Firbank SJ, Rogers MS, Wilmot CM, Dooley DM, Halcrow MA, Knowles PF, McPherson MJ, Phillips SE; Proc Natl Acad Sci U S A. 2001;98:12932-12937. PMID:11698678

2: Cyclomaltodextrinase, neopullulanase, and maltogenic amylase are nearly indistinguishable from each other. Lee HS, Kim MS, Cho HS, Kim JI, Kim TJ, Choi JH, Park C, Lee HS, Oh BH, Park KH; J Biol Chem. 2002;277:21891-21897. PMID:11923309

3: Structure, specificity and function of cyclomaltodextrinase, a multispecific enzyme of the alpha-amylase family. Park KH, Kim TJ, Cheong TK, Kim JW, Oh BH, Svensson B; Biochim Biophys Acta. 2000;1478:165-185. PMID:10825529

4: Oligo-1,6-glucosidase and neopullulanase enzyme subfamilies from the alpha-amylase family defined by the fifth conserved sequence region. Oslancova A, Janecek S; Cell Mol Life Sci. 2002;59:1945-1959. PMID:12530525

5: Pullulan degrading enzymes of bacterial origin. Doman-Pytka M, Bardowski J; Crit Rev Microbiol. 2004;30:107-121. PMID:15239382

6: Crystal structure of a free radical enzyme, galactose oxidase. Ito N, Phillips SE, Yadav KD, Knowles PF; J Mol Biol. 1994;238:794-814. PMID:8182749