Artificial enzyme

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 [http://www.pharm.uu.nl/ffwuk.htm?/medchem/] 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 [http://www.rsc.org/Publishing/Journals/CC/article.asp?doi=b709400k] .