Genetic Engineering to Boost Enzyme Reactions

Think of enzymes as tiny biological lab assistants that help things along; they start reactions and give them a nudge in the right direction. They are active proteins that bind to substances and are involved in most of the reactions that take place in our body including digestion and turning food into energy, metabolism and cell regulation. Enzymes are also widely used in industry. Being catalysts they retain their state once the reaction is over.

Enzymes work by binding a substrate to its active site and reducing activation energy (the energy needed to start a reaction), which speeds up the rate of reaction. Enzymes are specific and only bind to certain substrates in a sort of "lock and key mechanism". They are sensitive and can only work under set conditions, so if the pH or temperature ranges that they operate in change they would be rendered ineffective.

The lock and key mechanism is not strictly true as enzyme and substrate are not rigid structures. The current model to explain how they fit together is the induced fit model, because substrate and enzyme active site both continue to change until they are completely bound to each other.

As powerful as enzymes are, it hasn't stopped scientists tweaking and playing around with them to enhance their use in industry. A team of scientists from Czech Republic, Germany and Japan have used genetic manipulation techniques to enhance the properties of an industrial enzyme. They claim that their work, which was published in Nature Chemical Biology in August 2009, has widespread applications in the chemical, medical and food industries.

They have come up with a way to speed up the reactions of enzymes involved in breaking down harmful waste chemicals from human activities. Previously researchers had concentrated their efforts on modifying the active site of the enzyme, but this new approach focused on parts of the enzyme known as the access tunnels. These structures connect the active site with the enzyme's surface.

The enzyme they manipulated degrades trichloropropane (TCP), a highly toxic colourless liquid. A by-product of chemical production it is a carcinogen that can stay in the soil and groundwater for more than 100 years. The new souped-up genetically enhanced enzyme was able to degrade the substance 32 times faster than a non-modified enzyme.

The researchers believe that the access tunnels of other enzymes could also be modified for a wide variety of industrial applications in many fields.

Martina Pavlova et al. Redesigning dehalogenase access tunnels as a strategy for degrading an anthropogenic substrate. Nature Chemical Biology, 5, 727 - 733 (2009); Published online 23 August 2009