Abstract:

Every biochemical reaction in the cell is catalysed by specific enzymes. Enzymes function in the same manner as do chemical catalysts, namely to lower the activation energy. Isolation of enzymes, either in a crude or purified form, permits biotransformation directly without the need for whole cells. In fact, biotransformations with isolated enzymes rather than cells as biocatalysts confer several advantages. High selectivity can be obtained with enzyme biocatalysts, because fewer by-products are produced, and many enzymes confer high degrees of regioselectivity.

By far the most common enzymes utilised in enzyme engineering to date have been extracellular and almost exclusively hydrolytic. These are relatively simple to extract and require little in the way of purification (Section 11.4). Even today, amylases¹ and proteases² are widely used in the food and beverage and detergent industries respectively.