RT Journal Article
SR Electronic
T1 Comparative Study of <em>ortho-</em> and <em>meta</em>-Nitrated Inhibitors of Catechol-<em>O</em>-methyltransferase: Interactions with the Active Site and Regioselectivity of <em>O</em>-Methylation
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 143
OP 153
DO 10.1124/mol.106.023119
VO 70
IS 1
A1 P. N. Palma
A1 M. L. Rodrigues
A1 M. Archer
A1 M. J. Bonifácio
A1 A. I. Loureiro
A1 D. A. Learmonth
A1 M. A. Carrondo
A1 P. Soares-da-Silva
YR 2006
UL http://molpharm.aspetjournals.org/content/70/1/143.abstract
AB In this work, we present a comparative case study of “ortho-” and “meta-nitrated” catecholic inhibitors of catechol-O-methyltransferase (COMT), with regard to their interaction with the catalytic site of the enzyme and the in vitro regioselective formation of their mono-O-methyl ether metabolites. In particular, the effects of altering the attachment position of the inhibitors' side-chain substituent, within the classic nitrocatechol pharmacophore, were investigated. For this purpose, we compared two simple regioisomeric nitrocatechol-type inhibitors of COMT, BIA 3-228 and BIA 8-176, which contain the benzoyl substituent attached at the meta and ortho positions, respectively, relative to the nitro group. The two compounds were slowly O-methylated by COMT in vitro, but the particular substitution pattern of each compound was shown to have a profound impact on the regioselectivity of their O-methylation. To provide a plausible interpretation of these results, a comprehensive analysis of the protein-inhibitor interactions and of the relative chemical susceptibility to O-methylation of the catechol hydroxyl groups was performed by means of docking simulations and ab initio molecular orbital calculations. The major structural and chemical factors that determine the enzyme regioselectivity of O-methylation were identified, and the X-ray structure of the complex of COMT with S-adenosyl-l-methionine and BIA 8-176 is herein disclosed. This is the first reported structure of the soluble form of COMT complexed with a nitrocatecholic inhibitor having a bulky substituent group in adjacent position (ortho) to the nitro group. Structural and dynamic aspects of this complex are analyzed and discussed, in the context of the present study.