High-Activity Mutants of Cocaine Esterase for Treatment of Drug Addiction

Enhancing cocaine metabolism by administration of cocaine esterases has been recognized as a promising treatment strategy for cocaine overdose and addiction. The esterase CocE is the most efficient native enzyme for metabolizing naturally occurring (-)-cocaine yet identified. Through catalysis of (-)-cocaine hydrolysis, CocE can both prevent and reverse extreme (-)- cocaine toxicity in rodent models and it has the potential to be developed into a chemically useful antagonist of the toxic and behavioral effects of (-)-cocaine. In order to optimize the efficacy of this potential anti-cocaine medication and minimize its possible side effects (particularly immunogenicity), we propose to improve the catalytic efficiency of CocE against (-)- cocaine. The higher the catalytic efficiency of the enzyme against (-)-cocaine, the lower the dose required to achieve therapeutic effectivness and the decrease in dose can reduce the overall immunological response. Hence we will focus on the rational design, discovery, and preclinical testing of CocE mutants with an improved catalytic efficiency against (-)-cocaine. The rational design of high-activity mutants of CocE against (-)-cocaine requires a detailed understanding of the mechanism for CocE-catalyzed hydrolysis of cocaine. This mechanism can be understood by performing computational studies using the state-of-the-art computational techniques of molecular modeling, simulation, and calculation. The specific aims include: (1) Elucidation of the detailed mechanism and reaction coordinate and the corresponding free energy profiles for CocE-catalyzed hydrolysis of cocaine by performing quantum mechanical (QM) calculations, hybrid quantum mechanical/molecular mechanical (QM/MM) calculations, and molecular dynamics (MD) simulations etc. (2) Design, discovery, and testing of CocE mutants with an improved catalytic efficiency against (-)-cocaine by using a recently developed novel computational design approach based on the transition state modeling and simulation to computationally evaluate a large number of hypothetical CocE mutants, followed by wet experimental tests including site-directed mutagenesis, protein expression and purification, and in vitro and in vivo activity tests. The long-term objective of this investigation will be to eventually develop an efficient anti-cocaine medication using a high-activity mutant of CocE.