X-ray Crystal Structure of a Bisubstrate Inhibitor Bound to the Enzyme Catechol-O-methyltransferase: A Dramatic Effect of Inhibitor Preorganization on Binding Affinity We thank F. Hoffmann–La Roche for generous support of this work. We are grateful to P. Malherbe for the cloning of COMT, P. Caspers for the expression of COMT, A. Cesura for enzyme purification, B. Wipf for fermentation, and H. W. Lahm for sequencing.

Abstract

With an IC50 value of 9 nM, 1 is the most potent known disubstrate inhibitor for catechol‐O‐methyltransferase (COMT). Inhibition of COMT is of significant interest in the therapy of Parkinsonapos;s disease since it ensures that a larger percentage of orally administered L‐dopa reaches—in the form of dopamine—its target in the brain. The X‐ray crystal structure of a complex formed by COMT and 1 has been solved at 2.6‐Å resolution.

Molecular Recognition in Chemical and Biological Systems

“…When the cocrystal structure of COMT bound to bisubstrate inhibitor 4 (IC 50 =9 n M , Figure 3 a) was solved, it became evident that a water molecule had been imported into the SAM nucleobase pocket, solvating N(6)H 2 and N(7) of adenine through moderately strong hydrogen bonding (Figure 3 b). 43b This water molecule did not show any polar contact to the protein. In a new series of ligands,45 with a 4‐fluorophenyl group replacing the NO 2 group on the catechol moiety, we introduced small alkyl substituents (Me, Et, Pr, c Pr, CH 2 CH 2 OH) on N(6) and solved the cocrystal structures for four of these complexes 45a.…”

“… a) Bisubstrate inhibitors of COMT 43b. 45a b) Structure of the adenosine binding site of the ternary complex of 4 with COMT and a Mg 2+ ion (2.6 Å resolution, PDB ID: 1JR4)43b showing the imported water molecule (W9). c) Binding mode of bisubstrate inhibitor 5 (1.30 Å resolution, PDB ID: 3HVH) 45a.…”

Multisubstrate adduct inhibitors: Drug design and biological tools

“…Only recently has the first effective bisubstrate COMT inhibitor been developed, and for this type of compound they used both the nucleoside and catechol moieties to bind the SAM and substrate enzyme binding sites 110,111 . This work was extended by synthesizing a new series of bisubstrate inhibitors reaching binding activities in the nanomolar range (Table 6) 112 .…”

Molekulare Erkennung in chemischen und biologischen Systemen

“…Nachdem die Cokristallstruktur von COMT mit gebundenem Bisubstratinhibitor 4 (IC 50 =9 n M , Abbildung 3 a) gelöst wurde, wurde ersichtlich, dass ein Wassermolekül in die SAM‐Nukleobasentasche eingeführt worden war, welches N(6)H 2 und N(7) vom Adeninteil des Inhibitors durch mäßig starke H‐Brücken solvatisiert (Abbildung 3 b). 43b Dieses Wassermolekül zeigte jedoch keine polaren Kontakte zum Protein. In einer neuen Ligandenserie,45 in der die Nitrogruppe am Catecholteil durch eine 4‐Fluorphenylgruppe ausgetauscht wurde, führten wir kleinere Alkylsubstituenten (Me, Et, Pr, c Pr, CH 2 CH 2 OH) am Adenin‐N(6) ein.…”

“… a) Bisubstratinhibitoren von COMT 43b. 45a b) Struktur der Adenosinbindungsstelle des ternären Komplexes von 4 mit COMT, einem Mg 2+ ‐Ion (2.6 Å Auflösung, PDB ID: 1JR4)43b und dem importierten Wassermolekül (W9). c) Bindungsmodus des Bisubstratinhibitors 5 (1.30 Å Auflösung, PDB ID: 3HVH) 45a.…”