Enzymes (high-molecular weight polymers of amino-acids) are biologically active proteins present in all living organisms. Enzymes are the catalysts of the living world that allow these organisms to reproduce, grow and finally live.
Microorganisms (bacteria, yeast, filamentous fungi) are now widely used as cell factories to produce these enzymes on an industrial scale. Each single microorganism harbors several thousand of different enzymes corresponding to specific transformations.
what are they?
Enzymes are linear polymeric chains of amino acid (100 to several thousands). There are 20 different natural amino acids, which makes a quasi-infinite number of combinations (20100 for a protein of 100 amino acids!).
The order in which the amino acids appear in a protein is called sequence and makes the primary structure.
Parts of proteins have distinct structural conformations named secondary structure, dependent on hydrogen bonding. The two main types of secondary structures are the α-helix and the ß-sheet.
The overall three-dimensional shape of an entire protein molecule is the tertiary structure. The protein molecule will bend and twist in order to achieve maximum stability or lowest energy state. The tertiary structure defines the active site of an enzyme. A change of a single amino acid may have huge consequences on their structure and consecutively their performances (positive or negative !)
how do they work?
Enzymes can catalyze biochemical reactions :
- The enzyme recognizes the substrate as a “lock and key” pair : enzymes are very specific and only work with certain substrates
- The substrate enters the active site of the enzyme
- The tertiary structure of the enzyme changes upon binding of the substrate
- The reaction begins, side chains of the amino acids of the active site play the role of catalysts
- The substrate is changed into a product
- The product is released from the enzyme. The enzyme returns to initial state and is ready for another reaction
When does the reaction stop? When the reactants (the product and the substrate) reach what is called “equilibrium” or when the enzyme becomes inactive.
Enzymes can stand a very wide range of activity conditions (temperature, pH, pressure…), or even work in pure organic solvents.
As catalysts, they improve the efficiency and economics of biochemical reactions. Notably, enzymes are specific (regio- and stereoselectivity), and proven to be very competitive while applied to synthetize complex or chiral molecules.
Several techniques do exist to optimize the enzymes performances :
- Molecular biology and protein engineering, to fine-tune enzymes’ catalytic activities, or design non-natural reactions
- Formulation (drying, immobilization…) to increase their robustness and operability
Finally, enzymes are biodegradable, and can be efficient in mild conditions. As such, they fully comply with the principles of Green Chemistry, and are often selected to replace organometallic catalysts. They are commonly applied to produce:
- chemical building blocks (amino-acids, organic acids…)
- Aromas and Perfumes
- Active pharmaceutical ingredients…