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An artificial enzyme is a synthetic, organic molecule prepared to recreate the active site of an enzyme.
Enzyme catalysis of chemical reactions occur with high selectivity and rate in a small part of the enzyme macromolecule known as the active site. There, the binding of a substrate close to functional groups in the enzyme causes catalysis by so-called proximity effects. It is therefore possible to create similar catalysts from small molecule mimics of enzyme active sites by combining, in a small molecule, the ability to bind substrate with catalytic functional groups. Since the artificial enzymes need to bind molecules, they are made based on a host-molecule such as a cyclodextrin, crown ethers or calixarene etc.
A number of artificial enzymes have been reported catalysing various reactions with rate increases up to 103; this is nevertheless substantially lower than natural enzymes that typically causes rate increases above 106. One of the pioneers in artificial enzyme research is chemist Ronald Breslow.
New approaches based on amino acids or peptides as characteristic molecular moieties have led to a significant expansion of the field of artificial enzymes or enzyme mimics. For instance, recent results by the group of Rob Liskamp have shown that scaffolded histidine residues can be used as mimics of certain metalloproteins and -enzymes. Especially the structural mimicry of certain copper proteins (e.g. hemocyanin, tyrosinase and catechol oxidase), containing so-called type-3 copper binding sites, has been shown. This is a significant improvement since the use of scaffolded histidine residues is one step closer to the mimicry of enzymes by biological relevant species such as amino acids and peptides.