Transaminases organic solvents

Tmppo, M.D., Strotman, H., and Hughes, G. (2012) Development of an immobilized transaminase capable of operating in organic solvent. ChemCatChem, 4, 1071-1074. 

The transaminase was used in organic solvents (35% dimethylformamid) as a cosolvent to increase substrate concentration due to the low solubility in water. A 100-fold molar excess of 2-propylamine as the amino donor (IM) was used, leading to conversion rates of 85-89% and ee of 90-96%. 

Most enzymes require an aqueous environment for their best performances. This is in conflict with the current need for transaminases with a wide substrate specihcity including poorly water-soluble molecules. To enhance the solubility of these substrates, cosolvents like DMSO have to be added. Besides this, organic solvents are deployed for product extrachon to avoid product inhibition. Using transaminases in neat organic solvents does not require continuous pH control and addihonal product extrachon. 

Only a few studies have been published, examining the stability and activity of transaminases in organic solvents to overcome product inhibition and to expand the substrate spectrum of transaminases [44,57,151,152]. 

Recently immobilized transaminases in neat organic solvents have been examined for the asymmetric synthesis of amines [153]. The immobilization of the co-transaminase with Sepabeads was carried out by incubation of the transaminase with the beads in buffer for 48 h. By means of the enzyme achvity, the screening of several organic solvents was carried out among which isopropyl acetate was the most suitable solvent. The immobilized enzyme showed high activity and stability under the chosen reachon conditions, as well as good yields of various tested amines. 

---