Synthetic Enzymes

One branch of synthetic biology deals with the fabrication of enzymes that evolution would have never made. This is important because life, while perfectly adapted to nature, is not prepared for industrial processes. The process of enzyme engineering is used to create and improve upon computer generated enzyme models. Afterwards the genetic information in bacteria is altered to match the amino acid combinations of the computer model. Those bacteria will then produce the enzyme  ‘created’ by the engineers for their use.

Because this modern technology was not at our disposal, we fell back on another method for the production of ‘our’ enzyme. The principle upon which this method is based is the fact that it is possible to expand on the canon amino acids: when the nutrient solution of a special, specific bacteria is deprived of a standard amino acid and supplemented with a non-canon amino acid that has a similar structure, it is likely  that the amino acid that has been ‘smuggled in’ will be used for protein synthesis.  The result, in this case, might be an enzyme that has a modified structure and, therefore, new properties. It must be stated that this method only works with a small number of bacterial strains. An Example is GFP, green fluorescent protein, which was first isolated in 1961 by the Japanese scientist Osama Shimomura in the jellyfish

Picture: Ethionin

Aequorea victoria. This protein allows the organism that carries it to glow green under the influence of UV light. When this protein is connected to other enzymes, intracellular processes – such as the splitting of the cell nucleus and the connected doubling of chromosome sets– can be observed under a microscope. GFP can be made to glow yellow or cyan through reprogramming. With the implementation of non-canon amino acids, other colors (such as gold) can be achieved. This was first accomplished by the famous scientist Dr. Nedilko Budisa of MPI, our project partner and mentor.  A further example from Dr. Budisa’s work group is the synthetic lipase.
One after another, amino acids were switched out until 14 non-natural materials were stitched into the enzyme and because of this its level of activity even at very low temperatures was greatly increased.

When one considers how much diversity can be found in nature with only the 20 amino acids available and what kind of possibilities are hidden within the approximately 680 unused amino acids, it is easy to understand the role that protein

engineering aka synthetic biology could have in the future.

The non-canon amino acids Norleucine and Ethionine are used in the analysis of protein structures and functions. Aminoacyl-tRNA-Synthetases, enzymes important for protein synthesis, can be fooled by offering them non-biological amino acids instead of their normal substrates. That is how ethionine and norleucine are inserted into the positions usually reserved for Methionine.

We attempted to alter our catalase with these two amino acids.

Picture: Norleucin

adapted from
http://de.wikipedia.org/wiki/Norleucin