Molecular Engineering

Molecular engineering is a term loosely used to describe the design of enzymes using modern molecular biological techniques to alter their catalytic action. Examples include the following:

> Site-directed mutagenesis - In this technique, the DNA coding sequence for an enzyme is altered to change one or more amino acids in an enzyme when the mutated DNA is expressed in an organism.

> Hybrid enzymes - Here, molecular techniques allow researchers to put together two different biomolecules to make a fusion molecule with new, useful properties. Figure 11.28 depicts a hybrid enzyme made in this fashion. In this case, an oligonucleotide of a defined sequence has been grafted onto the enzyme staphylococcal nuclease. The specific sequence in the hybrid enzyme allows it to bind to a specific complementary nucleic acid sequence (specified by the bound oligonucleotide) and cut specifically at that point. The native, unaltered enzyme has no such specificity.

> Catalytic antibodies - These interesting molecules are antibodies with a very specific binding site to the transition state of an enzymatic reaction. The resulting molecules, called abzymes, act like antibodies. In some cases, abzymes can speed up reaction rates as much as 107-fold over the uncatalyzed reaction. The stereospecificity of enzymes (including abzymes) may provide a tremendous aid to the synthesis of stereospecific compounds in organic chemistry.

See also: Antibodies, Ribozymes

INTERNET LINKS:

> 1. Site-Directed Mutagenesis PCR Protocol

> 2. Site-Directed Mutagenesis Using the DUT-UNG System