Asymmetric synthesis of a fluoxetine precursor with an artificial fusion protein of a ketoreductase and a formate dehydrogenase

Herein we describe the kinetic characterization of a fusion protein from the 3-ketoacyl-[acyl-carrier-protein]-reductase (KR) from Synechococcus PCC 7942 and a mutant formate dehydrogenase from Mycobacterium vaccae N10 (MycFDH). Upon purification, a specific proteolytic cleavage of the MycFDH was observed. The cleavage site was elucidated, which is ubiquitously spread among prokaryotic FDHs. After depletion of the cleavage site the correct, full length fusion protein was obtained. In asymmetric reductions of ethylbenzoyl acetate (EBA) this fusion protein performed equal or even better than the free enzymes, yielding up to 39% more of the fluoxetine precursor ethyl-(S)-3-hydroxy-3-phenylpropanoate ((S)-HPPE). The rate acceleration is due to an improved K-m,K-EBA of the KR subunit. (C) 2014 Elsevier Ltd. All rights reserved.