An ene reductase from Clavispora lusitaniae for asymmetric reduction of activated alkenes

• A new ene reductase (ClER) from Clavispora lusitaniae is presented.
• ClER was active toward a diverse range of activated alkenes.
• As much as 500 mM ketoisophorone was reduced to (R)-levodione with 98% ee.

A putative ene reductase gene from Clavispora lusitaniae was heterologously overexpressed in Escherichia coli, and the encoded protein (ClER) was purified and characterized for its biocatalytic properties. This NADPH-dependent flavoprotein was identified with reduction activities toward a diverse range of activated alkenes including conjugated enones, enals, maleimide derivative and α,β-unsaturated carboxylic esters. The purified ClER exhibited a relatively high activity of 7.3 U mgprot−1 for ketoisophorone while a remarkable catalytic efficiency (kcat/Km = 810 s−1 mM−1) was obtained for 2-methyl-cinnamaldehyde due to the high affinity. A series of prochiral activated alkenes were stereoselectively reduced by ClER furnishing the corresponding saturated products in up to 99% ee. The practical applicability of ClER was further evaluated for the production of (R)-levodione, a valuable chiral compound, from ketoisophorone. Using the crude enzyme of ClER and glucose dehydrogenase (GDH), 500 mM of ketoisophorone was efficiently converted to (R)-levodione with excellent stereoselectivity (98% ee) within 1 h. All these positive features demonstrate a high synthetic potential of ClER in the asymmetric reduction of activated alkenes.