Highly sensitive and rapid detection of antibody catalysis by luminescent bacteria

Enzyme assays

Enzyme assays are analytical tools to visualize enzyme activities. In recent years a large variety of enzyme assays have been developed to assist the discovery and optimization of industrial enzymes, in particular for "white biotechnology" where selective enzymes are used with great success for economically viable, mild and environmentally benign production processes. The present article highlights the aspects of fluorogenic and chromogenic substrates, sensors, and enzyme fingerprinting, which are our particular areas of interest.

Screening systems

Enzyme screening technology has undergone massive developments in recent years, particularly in the area of high-throughput screening and microarray methods. Screening consists of testing each sample of a sample library individually for the targeted reaction. This requires enzyme assays that accurately test relevant parameters of the reaction, such as catalytic turnover with a given substrate and selectivity parameters such as enantio- and regioselectivity. Enzyme assays also play an important role outside of enzyme screening, in particular for drug screening, medical diagnostics, and in the area of cellular and tissue imaging. In the 1990s, methods for high-throughput screening of enzyme activities were perceived as a critical bottleneck. As illustrated partly in this chapter, a large repertoire of efficient screening strategies are available today that allow testing of almost any reaction with high-throughput.

Experimental determination of the absolute enantioselectivity of an antibody-catalyzed Diels-Alder reaction and theoretical explorations of the origins of stereoselectivity

The exo and endo Diels-Alder adducts of p-methoxycarbonylbenzyl trans-1,3-butadiene-1-carbamate and N,N-dimethylacrylamide have been synthesized, and the absolute configurations of resolved enantiomers have been determined. On the basis of this information, the absolute enantioselectivities of the Diels-Alder reaction catalyzed by antibodies 13G5 and 4D5 as well as other catalytic antibodies elicited in the same immunizations have been established. The effects of different arrangements of catalytic residues on the structure and energetics of the possible Diels-Alder transition states were modeled quantum mechanically at the B3LYP/6-311++G**//B3LYP/6-31+G** level of theory. Flexible docking of these enantiomeric transition states in the antibody active site followed by molecular dynamics on the resulting complexes provided a prediction of the transition-state binding modes and an explanation of the origin of the observed enantioselectivity of antibody 13G5.

High-throughput screening for biocatalysts

Recent progress in high-throughput enzyme assays includes new examples of fluorogenic and chromogenic substrates, fluorescence resonance energy transfer substrates, and applications of the pH and pM indicator methods. Recent developments of Horeau's pseudo-enantiomer derivatisation method to screen enantioselectivities in high-throughput have also been reported.