4Bioengineering.com

The Arnold laboratory is a world leader in the directed evolution and optimization of enzymes for applications in biotechnology. Biological systems have evolved over billions of years to perform very specific biological functions and to do so within the context of a living organism.

Some of the features required for function in a complex chemical network are undesirable when the catalyst is lifted out of context. Conversely many of the properties we wish enzymes would have clash with the needs of the organism, or at least were never required. The Arnold group is developing and using methods of directed evolution to explore the vast space of novel enzyme functions never explored in nature.

One very successful example has been the directed evolution of an enzyme to carry out the hydrolysis of a para-nitrobenzyl ester of an antibiotic (Moore & Arnold, Nature Biotechnology 14, 458-467 (1996) and Moore et al., J. Molecular Biol. 272, 336-347 (1997)). By applying sequential generations of random mutagenesis, recombination and screening, the enzyme’s catalytic efficiency was increased more than 100-fold.

More recently we evolved a cytochrome P450 monooxygenase to no longer require its ancillary electron-transfer proteins or any external cofactor (NADH) (Joo et al., Nature 399, 670-673 (1999)). The evolved enzymes hydroxylates its substrate using hydrogen peroxide rather than molecular oxygen, via the “peroxide shunt” pathway. While yielding powerful new catalysts for important synthetic reactions, this work clearly demonstrates that enzymes can acquire capabilities not found in naturally occurring organisms.