Ildiko M. Kovach, Ordinary Professor
Bioorganic, Physical Biochemistry
(202) 319-6550
kovach@cua.edu

B. S., 1964, Szemmelweisz University of Medical Sciences, Budapest, Hungary. Ph. D., 1974, University of Kansas. Postdoctoral Fellow, 1974-1978, University of Kansas. Editor and Member of the Editorial Board of the Biochemical Journal, England. Senior Fulbright Lecturing Award, 2003-2004 host institute Department of Biochemistry at Eotvos Lorand University, Budapest, Hungary.

Acetylcholinesterase Studies

Summary of Research Interests

The most fundamental idea pursued in our research program is the general question of the origin and evolutionary progress of catalytic acceleration by enzymes. The level of molecular recognition and the catalytic potential of active functional groups in small proteins and serine protease enzymes are probed. Acetylcholinesterase as an evolutionarily highly developed catalyst is also the subject of many investigations aimed at evaluating the importance of optimization of the step for leaving group departure in hydrolytic enzymes and the sensitivity of the catalytic machinery to alterations in the electronic and steric environments of substrates and inhibitors. Organophosphorus inhibitors [R(R'O)P(O)X] of serine hydrolase enzymes are of particular interest because they are excellent probes of the scope and strategies of serine hydrolase catalysis.

Investigation of the occurrence and significance of proton bridges in the catalytic mechanism of haemostatic and thrombolytic enzymes, particularly in a-thrombin is studied under NIH support.  Solvent kinetic isotope effects, proton inventories, high resolution, low-field H NMR measurements and computational chemistry are the key tools in these studies.

Selected Publications

D. Zhang and I. M. Kovach Full and Partial Deuterium Solvent Isotope Effect Studies of a-Thrombin-Catalyzed Reactions of Natural Substrates,  J. Am. Chem. Soc. 127, 3760-3766  (2005).

E. J. Enyedy and I. M. Kovach  Proton Inventory Studies of a-Thrombin-catalyzed Reactions of Substrates with Selected P and P? Sites. J. Am. Chem. Soc. 126,  6017-6024 (2004). 

I. M. Kovach  Stereochemistry and Secondary Reactions in the Irreversible Inhibition of Serine Hydrolases by Organophosphorus Compounds. J. Physical Organic Chemistry 17, 602-614 (2004). 

A.S. Mildvan, M.A. Massiah, T.K. Harris, G.T. Marks, D.H. T. Harrison, C. Viragh, P. M. Reddy and I. M. Kovach  Short Strong Hydrogen Bonds on Enzymes: NMR and Mechanistic Studies. J. Mol. Structure 163-175, (2002).

P. M. Reddy and I. M. Kovach  Synthesis of chiral methyl 4-nitrophenyl alkylphosphonothioates: BF₃-Et₂O-catalyzed alcoholysis of phosphonamidothioates. Tetrahedron Letters 43, 4063-4066 (2002).

P. M. Reddy, C. Viragh and I. M. Kovach  Synthesis of Phenyl or 4-Nitrophenyl Methyl  b-Ketophosphonate Esters.  Phosphorus Sulfur and Silicon 177, 1-4, (2002).

 A.S. Mildvan, M.A. Massiah, T.K. Harris, G.T. Marks, D.H. T. Harrison, C. Viragh, P. M. Reddy and I. M. Kovach   Short Strong Hydrogen Bonds on Enzymes: NMR and Mechanistic Studies. J. Mol. Structure (2002).

I. M. Kovach   Inhibition of Serine Hydrolases by Organophosphorus Compounds. Biokemia XXV, 74-80 (Hungarian invited review) 2001.

I. J. Enyedy and I. M. Kovach, A. Bencsura, A Molecular Dynamics Study of Active-site Interactions with Tetracoordinate Transients in Acetylcholinesterase and its Mutants. Biochemical J. 353, 645-653 (2001).

M. A. Massiah, C. Viragh, P. M. Reddy, I. M. Kovach, J. Johnson, T. L. Rosenberry and A. S. Mildvan, Short, Strong Hydrogen Bonds at the Active Site of Human Acetylcholinesterase: ¹ H-NMR Studies.  Biochemistry 40,  5682-5690 (2001).

C. Viragh, T. K. Harris, P. M. Reddy, M. A. Massiah, A. S. Mildvan and I. M. Kovach, NMR Evidence for a Short, Strong Hydrogen Bond in the Mechanism of a Cholinesterase. Biochemistry 39, 16200-16205 (2000).  

E. Enyedy and I. M. Kovach, Reversible Modulation of Human Factor Xa  Activity by Phosphonate Ester: Media Effects.  Bioorg. Med. Chem. 8, 549-556 (2000).

C. Viragh, I. M. Kovach and Lewis Pannell,  Small Molecular Products of Dealkylation in Soman-inhibited Electric Eel Acetylcholinesterase. Biochemistry 38, 9557 (1999).

I. M. Kovach, Ligand and Active-Site Dependent P-O Versus C-O Bond Cleavage in Organophosphorus Adducts of Serine Hydrolases. Phosphorus, Sulfur and Silicon, 144-146, 537-540 (1999).

A. Saxena, C. Viragh, D. S. Frazier, I. M. Kovach, D. M. Maxwell,  O. Lockridge and B. P. Doctor, The pH Dependence of Dealkylation in Soman-inhibited Cholinesterases and Their Mutants: Further Evidence for a Push-Pull Mechanism. Biochemistry 37, 15086-15096 (1998).

I. J. Enyedy, I. M. Kovach and B. R. Brooks, Alternate Pathways for Acetic Acid and Acetate Ion Release from Acetylcholinesterase: A Molecular Dynamics Study.  J. Am. Chem. Soc. 120,  8043-8050 (1998).

I. M. Kovach and E. Enyedy , Active-site-dependent Elimination of 4-Nitrophenol from 4-Nitrophenyl Alkylphosphonyl Serine Protease Adducts. J. Am. Chem. Soc. 120, 258-263  (1998).

I. M. Kovach, R. Akhmetshin, I. J. Enyedy and C. Viragh A Selfconsistent Mechanism for Dealkylation in Soman-inhibited Acetylcholinesterase. Biochemical J. 324, 995-996 (1997).

C. Viragh, R. Akhmetshin, I. M. Kovach, and C. Broomfield, Unique Push-Pull Mechanism of Ageing in Soman-inhibited Acetylcholinesterase. Biochemistry 36, 8243-8252 (1997).

E. Enyedy and I. M. Kovach, Modulation of the Activity of Human α-Thrombin with Phosphonate Ester Inhibitors.   Bioorg. Med. Chem. 5, 1531-1541, (1997).

A. Bencsura, I. Enyedy and I. M. Kovach, Probing the Active Site of Acetylcholinesterase by Molecular Dynamics of its Phosphonate Ester Adducts. J. Am. Chem. Soc. 118, 8531-8541 (1996).

I. Enyedy, A. Bencsura and I. M. Kovach, Interactions in Tetravalent and Pentavalent Phosphonate Esters of Ser at the Active Site of Serine Enzymes.  Phosphorus, Sulfur, and Silicon 109-110, 249-252 (1996).

Q. Zhao and I. M. Kovach, Reversible Modification of Tissue-type Plasminogen Activator by Methylphosphonate Esters . Bioorg. Med. Chem 4, 523-529 (1996).

A. Bencsura, I. Enyedy and I. M. Kovach, Origins and Diversity of the Aging Reaction in Phosphonate Adducts of Serine Hydrolase Enzymes: What  Characteristics of the Active Site Do They Probe? Biochemistry 34, 8989-8999 (1995).

I. M. Kovach, N. Qian and A. Bencsura, Efficient Product Clearance through Exit Channels in Substrate Hydrolysis by Acetylcholinesterase. FEBS Lett. 349, 60-64 (1994).

A. Saxena, N. Qian, I. M. Kovach, A. P. Kozikowski, Y. P. Pang, D. C. Vellom, Z. Radic, D. Quinn, P. Taylor, and B. P. Doctor, Identification of Amino Acid Residues Involved in the Binding of Huperzine-A to Cholinesterases. Protein Sci., 1770-1778 (1994).

Q. Zhao, I.M. Kovach, A. Bencsura and  A. Papathanassiu, Enantioselective and Reversible Inhibition of Trypsin and α-Chymotrypsin by Phosphonate Esters. Biochemistry 33, 8128 (1994).

N. Qian and I. M. Kovach, Key Active Site Residues in the Inhibition of Acetylcholinesterases by Soman.  FEBS Lett. 336, 263 (1993).

I. M. Kovach, Q. Zhao, M. Keane and R. Reyes, Rate-Determining Carbonyl Hydration in the Intramolecular Hydrolysis of Phenacyl Phosphonate Esters: Isotopic Probes and Activation Parameters. J. Am. Chem. Soc.. 115, 10471 (1993).

I. M. Kovach, A.J. Bennet, J.A. Bibbs, and Q. Zhao, Nucleophilic and Protolytic Catalysis of Phosphonate Ester Hydrolysis: Isotope Effects and Activation Parameters. J. Am. Chem. Soc.  115, 5138 (1993).

I. M. Kovach Solution Dynamics of Phosphonate Ester Hydrolysis.  Phosphorus, Sulfur and Silicon 75, 131 (1993).

I. M. Kovach, L. McKay and D. Vander Velde, Diastereomeric Phosphonate Ester Adducts of Chymotrypsin: ³¹P-NMR  Measurements.  Chirality 5, 143 (1993).

I. M. Kovach and L. McKay  Reversible Modulation of Serine Protease Activity by Phosphonate Esters. Bioorg. Med. Chem. Lett. 2, 1735 (1992).

I. M. Kovach and D. Huhta  Comparative Study of the Charge Distribution in Tetravalent Carbonyl Transients and Organophosphorus Adducts of Trypsin. J. Mol. Struct. (Theochem 79) 233, 335 (1991).

I. M. Kovach, Competitive Irreversible Inhibition of Enzymes in the Presence of a Substrate: Scope and Limitations. J. Enzyme Inhibit. 4, 201 (1991).

I. M. Kovach, D. Huhta and S. Baptist  Active Site Interactions in Hydrated Trypsin-Organophosphate Adducts: A YETI Molecular Mechanics Study.  J. Mol. Struct. (Theochem 72) 226, 99 (1991).

I. M. Kovach, Son Do and R.L. Schowen β-Secondary Deuterium Isotope Effect and Solvent Isotope Effects in Catalysis by Subtilisin BPN'. J. Phys. Org. Chem. 3, 260  (1990).

I. M. Kovach and A.J. Bennet Comparative Study of Nucleophilic and Enzymic Reactions of 2-Propyl Methylphosphonate Derivatives. Phosphorus, Sulfur and Silicon 51/52, 51 (1990).

ACS Publications

Recent presentations 

?Short Strong Hydrogen Bonds at the Active Site of Cholinesterases: ¹H-NMR Studies?  I. M. Kovach, C. Viragh, P. M. Reddy, M. A. Massiah, A. S. Mildvan, J. Johnson and T. L. Rosenberry, VIIth International Meeting on Cholinesterases, Pucon, Chile, November 8-12, 2002. 

?Full and Partial Deuterium Solvent Isotope Effect Studies of a-Thrombin-Catalyzed Reactions of Natural Substrates? D. Zhang and I. M. Kovach,  Isotopes 2005 Bath: An international conference, The University of Bath, UK, June 27- July 1, 2005. 

?Protonic Participation in the Rate-determining Step for the Hydrolysis of Fluorogenic Substrates Catalyzed by Hemostatic and Thrombolytic Enzymes.? I. M. Kovach, E. J. Enyedy and R. A. Akhmetshin, International  Isotope Effects Conference an EUCHEM Conference, Uppsala, Sweden, June 22-27, 2003.  

"Protonic Participation in Hemostatic and Thrombolytic Enzyme-catalyzed Reactions." I. M. Kovach, E.J. Enyedy and R.A. Akhmetshin, XVth  International Conference on Horizons in Hydrogen Bond Research, Freie Universitat Berlin, Germany, September 16-21, 2003.   

Awards    

.