Abstract
Enzymes have been used in organic chemistry and biotechnology for 100 years, but
their widespread application has been prevented by a number of limitations, including the often-
obser ved limited thermostability, narrow substrate scope, and low or wrong stereo- and/or
regioselectivity. Directed evolution provides a means to address and generally solve these problems,
especially since recent methodology development has made this protein engineering method faster,
more efficient, and more reliable than in the past. This Darwinian approach to asymmetric
catalysis has led to a number of industrial applications. Metabolic-pathway engineering,
mutasynthesis, and fermentation are likewise enzyme-based techniques that enrich chemistry. This
account outlines the scope, and particularly, the limitations, of biocatalysis. The complementary nature of enzymes and man-made catalysts is emphasized.
