KAIST CBE SPECIAL SEMINAR

Tuesday, October 1, 2013 / 10:00AM

Room 1101, W1-3 Bldg.

Two kinds of obstacles to novel biological catalysts: protein engineering and heterogeneous kinetics

Andreas S. Bommarius

School of Chemical and Biomolecular Engineering, School of Chemistry and Biochemistry,

Parker H. Petit Institute for Bioengineering and Bioscience

Georgia Institute of Technology

Biocatalysts are increasingly used in industry from processing of renewable raw materials to creating enantiomerically pure compounds for pharma.  Contemporary methods of protein engineering, such as applying rational design guided by mechanistic and structural knowledge, have greatly increased the ability to create novel enzyme functionality.

In pharma applications, we have developed a novel amine dehydrogenase (AmDH) with broad substrate specificity.  Expansion of its substrate specificity was achieved through several rounds of focused mutagenesis based on degenerate codons and a high-throughput screening assay for simplified, rapid evaluation of enzyme variants.  Novel activity was achieved toward a number of compounds while maintaining the enzyme’s native enantioselectivity.

Semi-synthetic beta-lactam antibiotics are synthesized enzymatically with the use of penicillin G acylase (PGA). PGA currently exhibits only weak diastereoselectivity towards racemic phenylglycine methyl ester (rac-PGME) as electrophile during ampicillin synthesis. We have found variants with diastereomeric excess (d.e.R) improved from 37% for the wild-type enzyme to 98% for our most selective mutant, betaPhe24Ala.

Cellulase-catalyzed hydrolysis of cellulose to glucose, important for the production of biofuels, is one of the most important biocatalytic processes in the coming years.  However, the kinetics of cellulose degradation is controversial to this day, as restricted diffusion, product inhibition, and influence of the properties of cellulose complicate the situation.  The presentation will cover our perspective and the corresponding experimental evidence, resulting in a kinetic rate law for cellulose with observable variables.