The big casting of enzymatic functions

glass ampoules and glass containers

The mankind flies to the moon, explores the universe – but still on earth there is much more unexplored matter than we are aware of. Bioprospecting is a discipline, where new products and processes are discovered based on natural resources. The big ideas and innovations for industrial processes are right in front of us – we just have to observe nature and – which is the difficulty – recognize them.

The principle of bioprospecting in the field of biocatalysis reminds us a bit of a casting for a good movie: You are looking for a special enzymatic function? Then give it a try and screen for it in a particular (unexplored) habitat. acib researchers used this principle and discovered two new proteins with an amine transaminase function.

An amine transaminase can transfer amino groups and convert amines into ketones and the other way around. This is important for the biological synthesis of building blocks that are further used for pharmaceuticals, fine chemicals and agrochemicals (e.g. plant protecting agents). By the discovery of stable natural enzymes, the production processes become much more environmentally friendly.

Let the “enzyme-casting” begin

Our researchers looked for “enantioselective” amine transaminase, meaning that also the structural orientation of the enzymatic substrate is considered. The methodology of choice was a combination of a sequence- and an activity based approach: The team extracted the DNA-sequence from an enriched soil sample full of microorganisms that are capable of using the target substrate, (R)-amine, as a sole nitrogen source. This implies that the enzymatic function of converting this (R)-amine is somewhere there. Then they aligned these sequences to the known sequence of amino acid transaminases in order to identify any similarities.

And the winner is …

Those enzyme sequences with a high similarity to the target enzymatic function passed the “Casting” and where further explored in the wet-lab to determine their activity. Now it became clear which candidates are able to stand up to industrial process conditions, such as high temperatures, different pH conditions, salts etc. The two winners that came into the final have been CpuTA1 (pH8, KPi buffer, up to 30°C) and MgiTA1 (pH8, Tris/HCl buffer, up to 40°C).

The subsequent exploration of the particular enzyme structures finally enabled our researchers to identify a completely new subclass of amino transferases! We keep you posted about how the winners behave under process conditions in future – in the meantime we refer to Nature.

This blog bases on the following paper: 
T Pavkov-Keller, GA Strohmeier, M Diepold, W Peeters, N Smeets, M Schürmann, K Gruber, H Schwab, K Steiner: Discovery and structural characterization of new fold type IV transaminases exemplify the diversity of this enzyme fold. 2016 Nature, Scientific reports 6, 38183, DOI 10.1038/srep38183  
Picture credits: acib