From Semirational to Rational Design: Developing a Substrate-Coupled System of Glucose Dehydrogenase for Asymmetric Synthesis

Glucose dehydrogenase (GDH) generally functions as an expensive cofactor NAD(P)H regenerator in an enzyme-coupled cofactor regeneration system, as in the production offine chemicals. However, whether GDH can accept substrates otherthan glucose remains to be explored. Based on a known mutant of GDH with high thermostability, DN46 (E170K-K252L), weemployed semirational design-based directed evolution to expand its substrate scope and promote its application in the asymmetricsynthesis of methyl 2-hydroxyl carboxylates. After one round of saturation mutagenesis and two rounds of iterative saturationmutagenesis, an enantioselectivity-enhanced mutant DN46-E96Q-H147V (>99% ee,R-preference) and enantioselectivity-reversedmutant DN46-E96Q-I150A-W152L with high enantioselectivity (>97% ee,S-preference) evolved. With glucose as a cosubstrate, wedeveloped a dual-function GDH-based substrate-coupled cofactor regeneration system for asymmetric synthesis. Furthermore, inlight of a deeper understanding of the catalytic mechanism, a rational design was successfully performed to create a mutant DN46-W152G for the upscaled synthesis of (R)-2-chloromandelic acid methyl ester, the precursor of the medicine (S)-clopidogrel. Thiswork expands the utilization of GDH, provides a design method for rational design of this enzyme, and will support future workregarding its application toward achieving even broader substrate scope

Automated summary

Glucose dehydrogenase (GDH) can be modified through directed evolution to expand its substrate scope and enantioselectivity, allowing for its application in asymmetric synthesis. Rational design based on understanding of the catalytic mechanism can further enhance its utility for pharmaceutical synthesis.