title: Mechanistic study of the reaction of thiol-containing enzymes with alpha,beta-unsaturated carbonyl substrates by computation and chemoassays.
abstract: We investigated the reactions between substituted alpha,beta-unsaturated carbonyl compounds (Michael systems) and thiols by computations as well as chemoassays. The results give insight into variations in the underlying mechanisms as a function of the substitution pattern. This is of interest for the mechanisms of inhibition of the SARS coronavirus main protease (SARS-CoV M(pro)) by etacrynic acid derivatives as well as for the excess toxicity of substituted alpha,beta-unsaturated carbonyl compounds. This study compares possible reaction courses including 1,4-addition followed by a ketonization step, and underscores the importance of a base-catalyzed step for the reactivity of thiol groups in enzymes. Phenyl and methyl substituents at the Michael system decrease the reactivity of the electrophilic compound, but chlorophenyl substituents partly recover the reactivity. Computations also indicate that electron-pushing substituents lead to a change in the reaction mechanism. The conformation of the Michael system is also found to significantly influence reactivity: the s-cis conformation leads to higher reactivity than the s-trans conformation. The computed data explain the trends in measured inhibition potencies of substituted alpha,beta-unsaturated carbonyl compounds and of reaction rates in chemical assays. They also indicate that the reversibility of inhibition does not stand in contrast to the formation of a new covalent bond between inhibitor and protease.
authors.affiliation: Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Paasche
authors.forename: Markus
authors.initials: M
authors.lastname: Schiller
authors.forename: Tanja
authors.initials: T
authors.lastname: Schirmeister
authors.forename: Bernd
authors.initials: B
authors.lastname: Engels
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D004791:Enzyme Inhibitors / Q000737:chemistry*; D004798:Enzymes / Q000737:chemistry* / Q000378:metabolism; D007659:Ketones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D000447:Aldehydes; D004791:Enzyme Inhibitors; D004798:Enzymes; D007659:Ketones; D013438:Sulfhydryl Compounds
references.citation: J Org Chem. 2005 Jan 7;70(1):233-7
references.pmid: 15624927
references.citation: J Org Chem. 2009 Jul 3;74(13):4878-81
references.pmid: 19485345
references.citation: Curr Top Med Chem. 2006;6(4):331-53
references.pmid: 16611146
references.citation: J Gen Virol. 2000 Apr;81(Pt 4):853-79
references.pmid: 10725411
references.citation: J Med Chem. 2006 Aug 10;49(16):4971-80
references.pmid: 16884309
references.citation: Chemphyschem. 2006 Jun 12;7(6):1229-34
references.pmid: 16683282
references.citation: J Phys Chem A. 2008 Oct 16;112(41):10405-12
references.pmid: 18800781
references.citation: Chem Res Toxicol. 2009 Apr;22(4):742-50
references.pmid: 19317512
references.citation: Bioorg Med Chem. 2005 Sep 1;13(17):5240-52
references.pmid: 15994085
references.citation: J Am Chem Soc. 2001 Jun 13;123(23):5557-62
references.pmid: 11389639
references.citation: Nat Med. 2004 Dec;10(12 Suppl):S88-97
references.pmid: 15577937
references.citation: Biochemistry. 2004 Apr 20;43(15):4568-74
references.pmid: 15078103
references.citation: Bioorg Med Chem. 2004 May 1;12(9):2219-23
references.pmid: 15080921
references.citation: J Phys Chem B. 2008 May 1;112(17):5458-69
references.pmid: 18393547
references.citation: J Org Chem. 2009 Aug 7;74(15):5244-9
references.pmid: 19719251
references.citation: Chem Res Toxicol. 2005 Feb;18(2):330-41
references.pmid: 15720140
references.citation: J Phys Chem B. 2009 Apr 16;113(15):5282-9
references.pmid: 19301885
references.citation: Phys Rev B Condens Matter. 1988 Jan 15;37(2):785-789
references.pmid: 9944570
references.citation: ChemMedChem. 2006 Sep;1(9):1021-8
references.pmid: 16933238
references.citation: J Phys Chem B. 2008 Sep 18;112(37):11798-808
references.pmid: 18712902
references.citation: J Am Chem Soc. 2005 Aug 10;127(31):11115-24
references.pmid: 16076219
references.citation: J Med Chem. 2005 Nov 3;48(22):6832-42
references.pmid: 16250642
references.citation: ChemMedChem. 2007 Jan;2(1):120-8
references.pmid: 17066390
references.citation: J Am Chem Soc. 2004 Feb 18;126(6):1781-93
references.pmid: 14871110
references.citation: Med Chem. 2005 Jul;1(4):361-70
references.pmid: 16789893
references.citation: Chem Res Toxicol. 2007 Mar;20(3):558-62
references.pmid: 17319700
references.citation: J Am Chem Soc. 2008 Jul 9;130(27):8696-705
references.pmid: 18557615
references.citation: Proc Natl Acad Sci U S A. 1999 Sep 28;96(20):11000-7
references.pmid: 10500114
references.citation: Chemistry. 2000 Aug 4;6(15):2854-64
references.pmid: 10985733
references.citation: Chem Rev. 2005 Oct;105(10):3561-612
references.pmid: 16218561
references.citation: J Comput Chem. 2010 Mar;31(4):665-70
references.pmid: 19557765
references.citation: Science. 2003 May 30;300(5624):1399-404
references.pmid: 12730501
references.citation: Lancet. 2003 Apr 19;361(9366):1319-25
references.pmid: 12711465
references.citation: Chem Rev. 1997 Feb 5;97(1):133-172
references.pmid: 11848867