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Dr. Zoran Radić

Structure/Activity Relationships and Catalytic Mechanisms of Cholinesterases

Zoran Radić

Zoran Radić, Ph.D.

Associate Adjunct Professor
Skaggs School of Pharmacy and Pharmaceutical Sciences
Research Advisor
University of Zagreb, Zagreb, Croatia


(858) 534-6841

Research Summary: Kinetics of Ligand Interaction, Substrate Turnover and Oxime Reactivation in Cholinesterases

Dr. Radić is a graduate of the University of Zagreb in Croatia where he started his research in acetylcholinesterase (AChE) reaction kinetics under mentorship of late Dr. Elsa Reiner, one of founding contributors in the field of cholinesterases. His interests in the AChE molecular structure brought him to the laboratory of Dr. Palmer Taylor at UCSD where he contributed to functional mapping of the AChE molecule using site directed mutagenesis and defined structural domains and amino acid residues critical for catalytic activity and ligand interaction. He proposed a common, simplified kinetic scheme and equation to describe acetylcholine (ACh) turnover by both AChE and its structurally and functionally close relative butyrylcholinesterase (BChE) that included both substrate inhibition of AChE and substrate activation of BChE, two prominent forms of deviation from Michaelis- Menten kinfkovarik etcs. Later this scheme and mechanism proved useful for the description of oxime reactivation kinetics of nerve agent organophosphate (OP) and OP pesticide conjugated AChE and BChE including positive allosteric modulation in reactivation of OP-BChE and negative allosteric modulation of OP-AChE conjugates. Dr. Radić developed intrinsic tryptophane fluorescence based assays as a valuable tool for in vitro monitoring of time resolved and equilibrium interactions of cholinergic ligands with native nicotinic acetylcholine receptor ligand binding domain surrogates, ACh binding proteins (AChBPs), as well as with AChE and BChE. This assay proved essential in functional characterization of one of tightest known, high affinity binding small molecule femtomolar AChE inhibitors developed in collaboration with Dr. Barry Sharpless of The Scripps Research Institute in La Jolla (TSRI). Dr. Radić leads, as a PI, several NIH funded international collaborative projects with researchers from TSRI (Dr. Barry K. Sharpless and Dr. Valery Fokin) and Institute for Medical Research and Occupational Health in Zagreb, Croatia (Dr. Zrinka Kovarik) and Oak Ridge National Laboratory (Dr. Andrey Kovalevsky) and University of Utah (Dr. Donald Blumenthal) towards development of novel, improved oxime reactivators of OP-AChE and OP-BChE conjugates, both in vitro and in vivo. Also, ongoing is collaboration with Dr. Jonah Cheung of the New York Structural Biology Center.

Academic Achievements

Education: B.Sc., M.Sc. and Ph.D. in Chemistry and in Biochemistry from University of Zagreb, Croatia.

Awards and Honors:2016 Spiridion Brusina Medal; New York Academy of Science Professional Member, IREX Graduate Student Fellow and Fulbright and Fogarty Postdoctoral Research Fellow at UCSD, La Jolla.

Leadership Experience: Treasurer, Croatian Society of Biochemistry and Molecular Biology (1990).

Teaching:Advanced Visualization of Drug-Macromolecule Structural Interactions (SSPPS elective), Visualization of macromolecules and their interactions with drugs in 3D (WARR 87); Enzymes: Kinetics and Reaction Mechanisms, (graduate course at University of Zagreb)

Key Contributions to Pharmaceutical Sciences

  • Outlined joint simplified kinetic scheme and model for substrate turnover by AChE and BChE.
  • Developed intrinsic tryptophane based assay for in vitro characterization of ligand interaction with AChBP, AChE and BChE.
  • Described allosteric modulation of oxime reactivation of OP-BChE conjugates as a basis for development of a new class of small molecule measures to counteract OP poisoning and improve associated therapy.

Selected Recent Publications (from >100 articles)

Kovarik Z et al. (2016) Catalytic soman scavenging by the Y337A/F338A acetylcholinesterase mutant assisted with novel site-directed aldoximes. Chem Res Toxicol 28:1036 – 1044.

Mangas I et al. (2016) Resolving pathways of interaction of mipafox and a sarin analog with human acetylcholinesterase by kinetics, mass spectrometry and molecular modeling approaches. Arch Toxicol. 90: 603-616

Kovalevsky A et al. (2016). Limitations in current acetylcholinesterase structure-based design of oxime antidotes for organophosphate poisoning. Ann N Y Acad Sci. 78: 41-49.

Potential Collaborative Programs with the Pharmaceutical Industry:

Drug discovery for therapy of OP intoxication.