Metabolic engineering of Escherichia coli to produce (2S, 3R, 4S)-4-hydroxyisoleucine.

The stereo-specific L-isoleucine-4-hydroxylase (L-isoleucine dioxygenase (IDO)) was cloned and expressed in an Escherichia coli 2Δ strain lacking the activities of α-ketoglutarate dehydrogenase (EC 1.2.4.2), isocitrate liase (EC 4.1.3.1), and isocitrate dehydrogenase kinase/phosphatase (EC 2.7.11.5). The 2Δ strain could not grow in a minimal-salt/glucose/glycerol medium due to the blockage of TCA during succinate synthesis. The IDO activity in the 2Δ strain was able to "shunt" destroyed TCA, thereby coupling L-isoleucine hydroxylation and cell growth. Using this strain, we performed the direct biotransformation of L-isoleucine into 4-HIL with an 82% yield.