Asymmetric enzymatic hydration of unactivated terminal alkenes by two promiscuous oleate hydratases mined from marine metagenome

Abstract

Enantiopure alcohols are very important chemicals as highly valuable building blocks in the synthesis of pharmaceuticals, agrochemicals and materials. The direct enantioselective hydration of unactivated 1-alkenes is a highly straightforward and atom economy approach to access chiral alcohols, though quite challenging in organic synthesis owing to low selectivity and many environmental concerns. Herein, two novel oleate hydratases (MmOAH1 and MmOAH2) were identified from marine metagenome via a sequence-based mining approach, and the two OAHs were functionally expressed in Escherichia coli T7, purified and characterized. Both of the two OAHs exhibited surprising highly promiscuous hydratase activity toward unactivated 1-alkenes when a carboxylic acid decoy molecule was involved in the reaction. Besides its natural substrate oleate acid, a series of unactivated 1-alkenes were converted to (S)-alcohols by using the resting cell of E. coli (MmOAH1) and E. coli (MmOAH2), moderate to good conversions (6–90%) and excellent ee (>98%) were obtained. Preparative-scale experiments were also demonstrated with 1-decene and 1-tridecene, affording (S)-2-decanol and (S)-2-tridecanol in good yields and excellent ee (>99%). This study expands the biocatalytic toolbox of available enzymes for asymmetric hydration reactions and proved that the OAHs mined from marine metagenome is promising for biotechnology application in production of chiral alcohols.