Artificial enzymes, “Chemzymes”: current state and perspectives

Abstract

Enzymes have fascinated scientists since their discovery and, over some decades, one aim in organic chemistry has been the creation of molecules that mimic the active sites of enzymes and promote catalysis. Nevertheless, even today, there are relatively few examples of enzyme models that successfully perform Michaelis-Menten catalysis under enzymatic conditions (i.e., aqueous medium, neutral pH, ambient temperature) and for those that do, very high rate accelerations are seldomly seen. This review will provide a brief summary of the recent developments in artificial enzymes, so called "Chemzymes", based on cyclodextrins and other molecules. Only the chemzymes that have shown enzyme-like activity that has been quantified by different methods will be mentioned. This review will summarize the work done in the field of artificial glycosidases, oxidases, epoxidases, and esterases, as well as chemzymes that catalyze conjugate additions, cycloadditions, and self-replicating processes. The focus will be mainly on cyclodextrin-based chemzymes since they have shown to be good candidate structures to base an enzyme model skeleton on. In addition hereto, other molecules that encompass binding properties will also be presented.

Comparison of stereochemical structures of cholesterol from different sources by HPLC

“…First five min of chromatograms of stored cholesterol samples by HPLC also exhibited small peaks in paralel with those of HPLC analysis with the addition of cyclodextrins. Since esterase, phosphatase, epoxidase and oxidase activity of cyclodextrins and cyclodextrin derivatives have been reported (11), it is possible to conclude therefore that addition of cyclodextrins to mobile phase might chemically alter cholesterol structure and therefore should be used with caution in stereoisomeric analysis of cholesterol.…”

Efficient and Versatile Modification of the Secondary Face of Cyclodextrins through Copper‐Catalyzed Huisgen 1,3‐Dipolar Cycloaddition

“…[2] However, the utility of native CDs has limitations due to their fixed hydrophobic cavity sizes; furthermore, the water-solubility of readily available native β-CD is poor, and the association constants (K a ) of the inclusion complexes are usually low. Chemical modifications could offer opportunities to access novel CD hosts with improved properties for various applications, such as for use as novel inclusion hosts for drug delivery, [3][4][5] catalysis, [6][7][8][9][10][11] building blocks in supramolecular assemblies, [12][13][14][15] amphiphilic molecules for gene delivery, [16][17][18][19][20][21][22] ligands for complexing metals, [23][24][25] scaffolds for generating glycoclusters for enhancing carbo-groups, such as alkyl, alkenyl, ester, carboxylic acid, amide, and alcohol, have been successfully incorporated on the secondary face of β-CD from the same starting material. These functionalized CD derivatives could be used as building blocks for further structural modification or as hosts for different applications.…”

Substantial Spatial Flexibility and Hydrogen Bonding within the Catalysis Exerted by Cyclodextrin Artificial Glycosidases

“…[2,3] The development of artificial enzymes is an interesting yet challenging task, [4] but through the use of modified CDs as macromolecular hosts, [5] we have recently seen the appearance of some of the first glycosidase mimics. [6] The cyclodextrins are cyclic α(1-4)glucopyranosides, i.e. circular structures comprised of 6 (for α-CD) or 7 (β-CD) alphabetically denominated glucose units which are connected in a ring, forming a cone-shaped macrostructure with an upper (primary) and lower (secondary) rim.…”