Studies of selective chemical catalysis by hydrolases

• Main Author: Grewal, Harjap Singh
• Other Authors: Kazlauskas, Romas J. (advisor)
• Format: Thesis
• Language: English
• Published: McGill University 2002
• Subjects: Chemistry; Organic; Antarc*; Antarctica
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78370

Hydrolase catalyzed reactions are used for selective chemical catalysis. With directed evolution, rational mutations and molecular modeling the selectivity of these hydrolases can be increased and the origin of selectivity determined. This study investigates four selective hydrolase catalyzed reactions. Using molecular modeling the unusual regioselectivity of Pseudomonas cepacia lipase (PCL) and the selectivity of Candida antarctica B lipase (CAL-B) in nucleoside acylation reactions has been attributed to the binding of the nucleoside base within the active site. The enantio-selectivity of Pseudomonas fluorescens esterase (PFE) has been improved using a rational approach to directed evolution and models to explain the origin of improved mutants has been produced. The enantioselectivity of the beta-lactam ring opening reaction by CAL-B has been attributed to unfavorable steric interaction of the substrate with Ile189 and a model has been proposed for an alcohol bridge between the catalytic histidine (His224) and the lactam amine. Finally, high acetyl selectivity of ThermoGen esterase E018b has been demonstrated and reaction conditions optimized.