Identification of a marine NADPH-dependent aldehyde reductase for chemoselective reduction of aldehydes

A putative aldehyde reductase gene from Oceanospirillum sp. MED92 was overexpressed in Escherichia coli. The recombinant protein (OsAR) was characterized as a monomeric NADPH-dependent aldehyde reductase. The kinetic parameters Km and kcat of OsAR were 0.89 ± 0.08 mM and 11.07 ± 0.99 s−1 for benzaldehyde, 0.04 ± 0.01 mM and 6.05 ± 1.56 s−1 for NADPH, respectively. This enzyme exhibited high activity toward a variety of aromatic and aliphatic aldehydes, but no activity toward ketones. As such, it catalyzed the chemoselective reduction of aldehydes in the presence of ketones, as demonstrated by the reduction of 4-acetylbenzaldehyde or the mixture of hexanal and 2-nonanone, showing the application potential of this marine enzyme in such selective reduction of synthetic importance.

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► A putative oxidoreductase from Oceanospirillum sp. MED92 was identified as a NADPH-dependent aldehyde reductase.
► This enzyme exhibits high activity toward a variety of substituted benzaldehydes and aliphatic aldehydes, but no activity for ketone functional group.
► It represents the first aldehyde reductase of marine origin.
► It effectively catalyzes the chemo-specific reduction of aldehydes in the presence of ketones, a synthetically useful transformation.