Co-evolution of activity and thermostability of an aldo-keto reductase KmAKR for asymmetric synthesis of statin precursor dichiral diols.
Aldo-keto reductase KmAKR-catalyzed asymmetric reduction offers a green approach to produce dichiral diol tert-butyl 6-substituted-(3R,5R/S)-dihydroxyhexanoates, which are important building blocks of statins. In our previous work, we cloned a novel gene of NADPH-specific aldo-keto reductase KmAKR (WT) from a thermotolerant yeast Kluyveromyces marxianus ZJB14056 and a mutant KmAKR-W297H/Y296W/K29H (Variant III) has been constructed and displayed strict diastereoselectivity towards tert-butyl 6-cyano-(5R)-hydroxy-3-oxohexanoate ((5R)-1) but moderate activity and stability. Herein, to further co-evolve its activity and thermostability, we performed semi-rational engineering of Variant III by using a combinational screening strategy, consisting of tertiary structure analysis, loop engineering, and alanine scanning. As results, the "best" variant KmAKR-W297H/Y296W/K29H/Y28A/T63M (Variant VI) was acquired, whose Km, kcat/Km towards (5R)-1 was 0.66 mM and 210.77 s-1 mM-1, respectively, with improved thermostability (half-life of 14.13 h at 40 °C). Combined with 1.5 g dry cell weight (DCW) L-1Exiguobacterium sibiricum glucose dehydrogenase (EsGDH) for NADPH regeneration, 4.5 g DCW L-1Variant VI completely reduced (5R)-1 of up to 450 g L-1 within 7.0 h at 40 °C, yielding the corresponding optically pure tert-butyl 6-cyano-(3R,5R)-dihydroxyhexanoate ((3R,5R)-3, >99.5% d.e.p) with a space-time yield (STY) of 1.24 kg L-1 day-1, and this was the highest level documented in literatures so far on substrate loading and STY of producing (3R,5R)-3. Besides (5R)-1, Variant VI displayed strong activity on tert-butyl 6-chloro-(5S)-hydroxy-3-oxohexanoate ((5S)-2). 4.5 g DCW L-1Variant VI completely reduced 400 g L-1 (5S)-2, within 5.0 h at 40 °C, yielding optically pure tert-butyl 6-chloro-(3R,5S)-dihydroxyhexanoate ((3R,5S)-4, >99.5% d.e.p) with a STY of 1.34 kg L-1 day-1. In summary, Variant VI displayed industrial application potential in statins biomanufacturing.
['Qiu|Shuai|S|', 'Cheng|Feng|F|', 'Jin|Ling-Jun|LJ|', 'Chen|Yi|Y|', 'Li|Shu-Fang|SF|', 'Wang|Ya-Jun|YJ|', 'Zheng|Yu-Guo|YG|']
D000074408:Aldo-Keto Reductases D002208:Caproates D004795:Enzyme Stability D000086183:Exiguobacterium D005656:Fungal Proteins D042843:Glucose 1-Dehydrogenase D007716:Kluyveromyces D062105:Molecular Docking Simulation D056004:Molecular Dynamics Simulation D009154:Mutation D015202:Protein Engineering D013696:Temperature
Co-evolution Aldo-keto reductase Dichiral diol Asymmetric reduction Biocatalysis