In vitro selection for enzymatic activity: a model study using adenylate cyclase

Tailor-made biocatalysts: combining thermodynamics, organic synthesis, molecular biology, biochemistry and microbiology for the design of enzyme selections

A general strategy for the isolation of catalysts for given chemical reactions was designed.

A first link between genes and their corresponding proteins was established by phage display: using Darwin's principles on evolution based on selection and amplification, rare protein molecules can then be selected for function from a large repertoire prior to their characterization by sequencing of their genes.

A second link was created between enzymes and their products. By making use of the chelate effect and of Inovirus particles as a chemical, affinity chromatography for the reaction product is then sufficient to isolate among 10⁶ to 10¹¹ proteins and their genes, the rare ones coding for catalysts of interest. The strategy for the parallel processing of information on the catalytic activity of variants from a large protein repertoire is highlighted in this review.

Phage display of combinatorial peptide libraries: application to antiviral research

Given the growing number of diseases caused by emerging or endemic viruses, original strategies are urgently required: (1) for the identification of new drugs active against new viruses and (2) to deal with viral mutants in which resistance to existing antiviral molecules has been selected. In this context, antiviral peptides constitute a promising area for disease prevention and treatment. The identification and development of these inhibitory peptides require the high-throughput screening of combinatorial libraries. Phage-display is a powerful technique for selecting unique molecules with selective affinity for a specific target from highly diverse combinatorial libraries. In the last 15 years, the use of this technique for antiviral purposes and for the isolation of candidate inhibitory peptides in drug discovery has been explored. We present here a review of the use of phage display in antiviral research and drug discovery, with a discussion of optimized strategies combining the strong screening potential of this technique with complementary rational approaches for identification of the best target. By combining such approaches, it should be possible to maximize the selection of molecules with strong antiviral potential.

Functional cloning by phage display

This review focusses on the isolation of proteins from genomic or cDNA expression products libraries displayed on phage. The use of phage display is highlighted for the characterization of binding proteins with diverse biological functions. Phage display is compared with another strategy, the yeast two-hybrid method. The combination of both strategies is especially powerful to eliminate false positives and to get information on the biochemical functions of proteins.

Selection strategies for improved biocatalysts

Enzymes have become an attractive alternative to conventional catalysts in numerous industrial processes. However, their properties do not always meet the criteria of the application of interest. Directed evolution is a powerful tool for adopting the characteristics of an enzyme. However, selection of the evolved variants is a critical step, and therefore new strategies to enable selection of the desired enzymatic activity have been developed. This review focuses on these novel strategies for selecting enzymes from large libraries, in particular those that are used in the synthesis of pharmaceutical intermediates and pharmaceuticals.

High-throughput screens and selections of enzyme-encoding genes

The availability of vast gene repertoires from both natural sources (genomic and cDNA libraries) and artificial sources (gene libraries) demands the development and application of novel technologies that enable the screening or selection of large libraries for a variety of enzymatic activities. We describe recent developments in the selection of enzyme-coding genes for directed evolution and functional genomics. We focus on HTS approaches that enable selection from large libraries (>10(6) gene variants) with relatively humble means (i.e. non-robotic systems), and on in vitro compartmentalization in particular.

Selection of an Active Enzyme by Phage Display on the Basis of the Enzyme's Catalytic Activity in vivo

We have developed a novel phage display method based on catalytic activity for the in vivo selection of an enzyme. To confirm the validity of our method and to demonstrate its potential utility, we used biotin protein ligase (BPL) from Escherichia coli as a model enzyme. We were able to demonstrate the potential value of our method by selective enrichment for the birA gene, which encodes BPL, in a mixed library. The presented method for in vivo selection should allow selection of various enzymes that catalyze modification of peptides or proteins, such as protein ligase, acetylase, kinase, phosphatase, ubiquitinase, and protease (including caspase). The method should be useful in efforts to analyze mechanisms of signal transduction, to find unidentified enzymes encoded by cDNA libraries, and to exploit artificial enzymes.

Directed enzyme evolution and selections for catalysis based on product formation

Enzyme engineering by molecular modelling and site-directed mutagenesis can be remarkably efficient. Directed enzyme evolution appears as a more general strategy for the isolation of catalysts as it can be applied to most chemical reactions in aqueous solutions. Selections, as opposed to screening, allow the simultaneous analysis of protein properties for sets of up to about 10(14) different proteins. These approaches for the parallel processing of molecular information 'Is the protein a catalyst?' are reviewed here in the case of selections based on the formation of a specific reaction product. Several questions are addressed about in vivo and in vitro selections for catalysis reported in the literature. Can the selection system be extended to other types of enzymes? Does the selection control regio- and stereo-selectivity? Does the selection allow the isolation of enzymes with an efficient turnover? How should substrates be substituted or mimicked for the design of efficient selections while minimising the number of chemical synthesis steps? Engineering sections provide also some clues to design selections or to circumvent selection biases. A special emphasis is put on the comparison of in vivo and in vitro selections for catalysis.