FIGURE 2. Reaction mechanism for GASC1 demethylation.
From the following article:
The putative oncogene GASC1 demethylates tri- and dimethylated lysine 9 on histone H3
Paul A. C. Cloos, Jesper Christensen, Karl Agger, Alessio Maiolica, Juri Rappsilber, Torben Antal, Klaus H. Hansen and Kristian Helin
Nature 442, 307-311(20 July 2006)
doi:10.1038/nature04837
a, 1: Fe(ii) is bound by residues His 190, Glu 192 and His 288. 2: 
-Ketoglutarate is bound. 3: Iron binds oxygen. 4: Oxidative decarboxylation of -ketoglutarate produces carbon dioxide, succinate and ferryl (Fe(iv) = O). 5: Ferryl hydroxylation of methylated K9 releases formaldehyde. 6: The histone tail and succinate leave the GASC1 molecule. b, Demethylation assay using a synthetic H3K9me3 peptide as substrate, in the presence or absence of cofactors. AA, ascorbic acid. KG, ketoglurate. c, Demethylation assay using histones as substrates in the presence of varying amounts of N-oxalylglycine. d, Formaldehyde produced by incubating a fixed amount of GASC1 (40 
g) with varying amounts of H3K9me3 peptide or the non-methylated peptide, measured using a demethylation–FDH-coupled assay28. The y axis shows absorbance values at 340 nm.
