TAC-scaffolded tripeptides as artificial hydrolytic receptors: a combinatorial approach toward esterase mimics

Albada, H.B. and Liskamp, R.M.J. (2008) TAC-scaffolded tripeptides as artificial hydrolytic receptors: a combinatorial approach toward esterase mimics. Journal of Combinatorial Chemistry, 10(6), pp. 814-824. (doi:10.1021/cc800065a)

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Abstract

In this report, we present the first library of tripodal synthetic receptor molecules containing three different, temporarily N-terminal protected peptide arms capable of performing hydrolytic reactions. To construct this library, the orthogonally protected triazacyclophane (TAC)-scaffold was used in the preparation of a split−mix library of 19 683 resin bound tripodal receptor molecules. For the construction of the peptide arms, three different sets of amino acids were used, each focused on one part of the catalytic triad as found in several families of hydrolytic enzymes. Therefore, in the sets of amino acids used to assemble these tripeptides, basic (containing His and Lys), nucleophilic (containing Ser and Cys), or acidic (containing Asp and Glu) amino acid residues were present. In addition, nonfunctional hydrophobic amino acid residues were introduced. Possible unfavorable electrostatic interactions of charged N-termini or their acetylation during screening were circumvented by trifluoroacetylation of the N-terminal amines. Screening was performed with a known esterase substrate, 7-acetoxycoumarin, which upon hydrolysis gave the fluorescent 7-hydroxycoumarin, leading to fluorescence of beads containing a hydrolytically active synthetic receptor. Although many synthetic receptors contain catalytic triad combinations, apparently, only a few showed hydrolytic activity. Sequence analysis of the active receptors showed that carboxylate-containing amino acids are frequently found in the acidic arm and that substrate cleavage is mediated by lysine (noncatalytic) or histidine (catalytic) residues. Kinetic analysis of resynthesized receptors showed that catalysis depended on the number of histidine residues and was not assisted by significant substrate binding.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Liskamp, Professor Robert
Authors: Albada, H.B., and Liskamp, R.M.J.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of Combinatorial Chemistry
ISSN:1520-4766
ISSN (Online):1520-4766

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