Oxidative C-H hydroxylation of methyl groups, followed by their removal from DNA, RNA or histones, is an epigenetic process critical to transcriptional reprogramming and cell fate determination. This reaction is catalyzed by Fe(II)-dependent dioxygenases using the essential metabolite 2-ketoglutarate (2KG) as a cofactor. Given that the human genome encodes for more than 60 2KG-dependent dioxygenases, assigning their individual functions remains a significant challenge. Here we describe a protein-ligand interface engineering approach to break the biochemical degeneracy of these enzymes. Using histone lysine demethylase 4 (KDM4) as a proof-of-concept, we show that the enzyme active site can be expanded to employ bulky 2KG analogues that do not sensitize wild type demethylases. We establish the orthogonality, substrate specificity and catalytic competency of the engineered demethylation apparatus in biochemical assays. We further demonstrate demethylation of cognate substrates in physiologically relevant settings. Our results provide a para-digm for rapid and conditional manipulation of histone deme-thylases to uncloak their isoform-specific functions.