Publications

• A catechol-O-methyltransferase that is essential for auditory function in mice and humans.

  Du X., Schwander M., Moresco E.M.Y., Viviani P., Haller C., Hildebrand M.S., Pak K., Tarantino L., Roberts A., Richardson H., Koob G., Najmabadi H., Ryan A.F., Smith R.J.H., Mueller U., Beutler B.

  We have identified a previously unannotated catechol-O-methyltranferase (COMT), here designated COMT2, through positional cloning of a chemically induced mutation responsible for a neurobehavioral phenotype. Mice homozygous for a missense mutation in Comt2 show vestibular impairment, profound sens ... >> More

  We have identified a previously unannotated catechol-O-methyltranferase (COMT), here designated COMT2, through positional cloning of a chemically induced mutation responsible for a neurobehavioral phenotype. Mice homozygous for a missense mutation in Comt2 show vestibular impairment, profound sensorineuronal deafness, and progressive degeneration of the organ of Corti. Consistent with this phenotype, COMT2 is highly expressed in sensory hair cells of the inner ear. COMT2 enzymatic activity is significantly reduced by the missense mutation, suggesting that a defect in catecholamine catabolism underlies the auditory and vestibular phenotypes. Based on the studies in mice, we have screened DNA from human families and identified a nonsense mutation in the human ortholog of the murine Comt2 gene that causes nonsyndromic deafness. Defects in catecholamine modification by COMT have been previously implicated in the development of schizophrenia. Our studies identify a previously undescribed COMT gene and indicate an unexpected role for catecholamines in the function of auditory and vestibular sense organs. << Less

  Proc. Natl. Acad. Sci. U.S.A. 105:14609-14614(2008) [PubMed] [EuropePMC]

• Multiple molecular forms of catechol-O-methyltransferase. Evidence for two distinct forms, and their purification and physical characterization.

  Huh M.M., Friedhoff A.J.

  Catechol-O-methyltransferase (COMT: EC 2.1.1.6) has been shown to exist in the soluble fraction of rat liver as two distinct molecular forms, designated COMT I and COMT II, which are separable by gel filtration, ion exchange chromatography, and sedimentation. The predominant form, COMT I, has a sm ... >> More

  Catechol-O-methyltransferase (COMT: EC 2.1.1.6) has been shown to exist in the soluble fraction of rat liver as two distinct molecular forms, designated COMT I and COMT II, which are separable by gel filtration, ion exchange chromatography, and sedimentation. The predominant form, COMT I, has a smaller Mr of about 24,000, as determined by gel filtration and sedimentation, and less negative charge, whereas the minor form, COMT II, has a larger Mr of about 47,500 and more negative charge. The COMT I and COMT II have been purified 450- and 205-fold, respectively, from rat liver by a newly developed procedure which gives homogeneous enzyme preparations with respect to catechol-methylating activities. The molecular properties of the predominant form, COMT I, were: s20,w, 2.7; D20,W, 10.5; Stokes radius, 20.1 A; f/fo, 1.08; and pI, 4.9. For the minor form, COMT II, the values were s20,w, 3.8; D20,w, 7.3; Stokes radius, 28.7 A; f/fo, 1.23; and pI, 4.8. Catechol-O-methyltransferase was found to exhibit tissue-specific isozymic patterns in the distribution of its two variant forms. In the rat tissues, the liver and kidney exhibited the presence of the two physically separable forms. Catechol-O-methyltransferase was also found as two distinct molecular forms in human tissues, including liver, brain, and placenta. The two forms of human catechol-O-methyltransferase were not distinguishable by the criteria of gel filtration from their counterparts in rat liver, indicating that the two molecular forms of human and rat liver catechol-O-methyltransferase are homologous. No interconversion of one molecular form of catechol-O-methyltransferase into the other was observed under experimental conditions employed. Available evidence indicates that the two molecular forms of catechol-O-methyltransferase are genetically dissimilar proteins. << Less

  J Biol Chem 254:299-308(1979) [PubMed] [EuropePMC]

• Comparative study of ortho- and meta-nitrated inhibitors of catechol-O-methyltransferase: interactions with the active site and regioselectivity of O-methylation.

  Palma P.N., Rodrigues M.L., Archer M., Bonifacio M.J., Loureiro A.I., Learmonth D.A., Carrondo M.A., Soares-da-Silva P.

  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. ... >> More

  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. << Less

  Mol. Pharmacol. 70:143-153(2006) [PubMed] [EuropePMC]

• The purification and properties of pig brain catechol-o-methyltransferase.

  Gulliver P.A., Tipton K.F.

  J Neurochem 32:1525-1529(1979) [PubMed] [EuropePMC]