Abstract
Initial velocity and product inhibition studies have been performed on soluble catechol-O-methyltransferase which has been partially purified from pig liver. The results are consistent with an ordered reaction mechanism, in which S-adenosyl-L-methionine (AdoMet) is the leading substrate. The enzyme is irreversibly inhibited by maleimide derivatives in a biphasic manner, which suggests a differential reaction with two thiol groups. N-(3,4-Dihydroxyphenyl)maleimide, which has a reactive moiety (maleimide ring) and an affinity moiety (catechol ring), acts as an affinity labelling compound on the more reactive SH group; AdoMet and Mg2+ protect against this modification. Total protection of this SH group results in a pseudo-first-order inhibition of the enzyme, with the apparent rate constant being proportional to the inhibitor concentration. All the other maleimide derivatives studied inhibited the enzyme by reacting with one of the two SH groups in a non-specific manner. The reaction of the other, more reactive, SH group was either specific (active-site-directed) or non-specific, depending on the substituent present in the affinity moiety and also on the length of an intermediate chain of methylene groups present between this moiety and the reactive maleimide ring. In the presence of both AdoMet and Mg2+, 3,5-dinitrocatechol, a reversible inhibitor of the enzyme which is competitive with respect to the catechol substrate, protects the enzyme from inactivation by any of the maleimide derivatives. The adducts of these maleimide derivatives formed with dithiothreitol inhibit the enzyme reversibly, showing inhibition patterns that are consistent with the mechanism deduced from the initial velocity and product inhibition studies.
Full text
PDF







Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- AXELROD J., TOMCHICK R. Enzymatic O-methylation of epinephrine and other catechols. J Biol Chem. 1958 Sep;233(3):702–705. [PubMed] [Google Scholar]
- Borchardt R. T., Bhatia P. Catechol O-methyltransferase. 12. Affinity labeling the active site with the oxidation products of 5,6-dihydroxyindole. J Med Chem. 1982 Mar;25(3):263–271. doi: 10.1021/jm00345a013. [DOI] [PubMed] [Google Scholar]
- Borchardt R. T. Catechol O-methyltransferase. 1. Kinetics of tropolone inhibition. J Med Chem. 1973 Apr;16(4):377–382. doi: 10.1021/jm00262a015. [DOI] [PubMed] [Google Scholar]
- Borchardt R. T., Smissman E. E., Nerland D., Reid J. R. Catechol O-methyltransferase. 7. Affinity labeling with the oxidation products of 6-aminodopamine. J Med Chem. 1976 Jan;19(1):30–37. doi: 10.1021/jm00223a007. [DOI] [PubMed] [Google Scholar]
- Borchardt R. T., Thakker D. R. Affinity labeling of catechol O-methyltransferase by N-haloacetyl derivatives of 3,5-dimethoxy-4-hydroxyphenylethylamine and 3,4-dimethoxy-5-hydroxyphenylethylamine. Kinetics of inactivation. Biochemistry. 1975 Oct 7;14(20):4543–4551. doi: 10.1021/bi00691a033. [DOI] [PubMed] [Google Scholar]
- Borchardt R. T., Thakker D. R. Catechol O-methyltransferase. 6. Affinity labeling with N-haloacetyl-3,5-dimethoxy-4-hydroxyphenylalkylamines. J Med Chem. 1975 Feb;18(2):152–158. doi: 10.1021/jm00236a008. [DOI] [PubMed] [Google Scholar]
- Borchardt R. T., Thakker D. R. Evidence for sulfhydryl groups at the active site of catechol-O-methyltransferase. Biochim Biophys Acta. 1976 Oct 11;445(3):598–609. doi: 10.1016/0005-2744(76)90113-3. [DOI] [PubMed] [Google Scholar]
- Cleland W. W. Statistical analysis of enzyme kinetic data. Methods Enzymol. 1979;63:103–138. doi: 10.1016/0076-6879(79)63008-2. [DOI] [PubMed] [Google Scholar]
- Coward J. K., Slixz E. P., Wu F. Y. Kinetic studies on catechol O-methyltransferase. Product inhibition and the nature of the catechol binding site. Biochemistry. 1973 Jun 5;12(12):2291–2297. doi: 10.1021/bi00736a017. [DOI] [PubMed] [Google Scholar]
- Flohe L., Schwabe K. P. Kinetics of purified catechol O-methyltransferase. Biochim Biophys Acta. 1970 Dec 16;220(3):469–476. doi: 10.1016/0005-2744(70)90278-0. [DOI] [PubMed] [Google Scholar]
- GOA J. A micro biuret method for protein determination; determination of total protein in cerebrospinal fluid. Scand J Clin Lab Invest. 1953;5(3):218–222. doi: 10.3109/00365515309094189. [DOI] [PubMed] [Google Scholar]
- Jeffery D. R., Roth J. A. Kinetic reaction mechanism for magnesium binding to membrane-bound and soluble catechol O-methyltransferase. Biochemistry. 1987 May 19;26(10):2955–2958. doi: 10.1021/bi00384a042. [DOI] [PubMed] [Google Scholar]
- Jeffery D. R., Roth J. A. Purification and kinetic mechanism of human brain soluble catechol-O-methyltransferase. J Neurochem. 1985 Mar;44(3):881–885. doi: 10.1111/j.1471-4159.1985.tb12898.x. [DOI] [PubMed] [Google Scholar]
- KITZ R., WILSON I. B. Esters of methanesulfonic acid as irreversible inhibitors of acetylcholinesterase. J Biol Chem. 1962 Oct;237:3245–3249. [PubMed] [Google Scholar]
- Nikodejevic B., Senoh S., Daly J. W., Creveling C. R. Catechol-O-methyltransferase. II. A new class of inhibitors of catechol-o-methyltransferase; 3,5-dihydroxy-4-methoxybenzoic acid and related compounds. J Pharmacol Exp Ther. 1970 Jul;174(1):83–93. [PubMed] [Google Scholar]
- Piedrafita F. J., Elorriaga C., Fernández-Alvarez E., Nieto O. Inhibition of catechol-O-methyltransferase by N-(3,4-dihydroxyphenyl) maleimide. J Enzyme Inhib. 1990;4(1):43–50. doi: 10.3109/14756369009030387. [DOI] [PubMed] [Google Scholar]
- RAY W. J., Jr, KOSHLAND D. E., Jr A method for characterizing the type and numbers of groups involved in enzyme action. J Biol Chem. 1961 Jul;236:1973–1979. [PubMed] [Google Scholar]
- Rivett A. J., Roth J. A. Kinetic studies on the O-methylation of dopamine by human brain membrane-bound catechol O-methyltransferase. Biochemistry. 1982 Apr 13;21(8):1740–1742. doi: 10.1021/bi00537a006. [DOI] [PubMed] [Google Scholar]
- Tunnicliff G., Ngo T. T. Kinetics of rat brain soluble catechol-O-methyltransferase and its inhibition by substrate analogues. Int J Biochem. 1983;15(5):733–738. doi: 10.1016/0020-711x(83)90200-8. [DOI] [PubMed] [Google Scholar]
- Zürcher G., Da Prada M. Rapid and sensitive single-step radiochemical assay for catechol-O-methyltransferase. J Neurochem. 1982 Jan;38(1):191–195. doi: 10.1111/j.1471-4159.1982.tb10871.x. [DOI] [PubMed] [Google Scholar]
