Catechol-O-methyltransferase in complex with substituted 3'-deoxyribose bisubstrate inhibitors

High-resolution structures of catechol-O-methyltransferase with ribose-modified inhibitors and Mg²⁺ identify the side chain of Glu90 as crucial for hydrogen bonding to the ribose hydroxyl groups. Glu90 subtly aligns with the 2'-hydroxyl, but not the 3'-hydroxyl, group to increase binding affinity, explaining the observed activities of bisubstrate inhibitors with a 3'-desoxyribose moiety.