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8 Enzyme Engineering and Technology 213

in routine laboratory practice, and others that are
used in clinical laboratory assays. This group also
includes a number of DNA and RNA modify-
ing enzymes (DNA and RNA polymerase, DNA lig-
ase, restriction endonucleases, reverse transcriptase,
etc.), which led to the development of molecular
biology methods and were a foundation for the
biotechnology industry (Yeo et al. 2004). The clever
application of one thermostable DNA polymerase
led to the polymerase chain reaction (PCR), and this
has since blossomed into numerous clinical, foren-
sic, and academic embodiments. Along with the
commercial success of these enzyme products, other
enzyme products are currently in commercial devel-
opment.

Another important field of application of enzymes

is in metabolic engineering. Metabolic engineering

is a new approach involving the targeted and pur-

poseful manipulation of the metabolic pathways of

an organism, aiming at improving the quality and

yields of commercially important compounds. It

typically involves alteration of cellular activities

by manipulation of the enzymatic functions of the

cell using recombinant DNA and other genetic

techniques. For example, the combination of ration-

al pathway engineering and directed evolution has

been successfully applied to optimize the pathways

for the production of isoprenoids such as carotenoids

(Schmidt-Dannert et al. 2000, Umeno and Arnold

2004).

Figure 8.22.Principal scheme of using CAAX-tagged proteins for covalent modification with prenyl transferases.