Alternative Dehydrogenases to Address Glucose Dehydrogenase Cross-Reactivity During NADPH Regeneration

Biocatalytic reductions require NAD(P)H generation, which is usually achieved using a glucose/glucose dehydrogenase (GDH) system. However, certain GDHs exhibit cross-reactivity by reducing various keto or iminium substrates during NADPH regeneration, thereby altering the stereoselectivity of the final products. In this study, we evaluated two established NADPH regeneration enzymes-phosphite dehydrogenase (PTDH) and isocitrate dehydrogenase (ICDH) for their potential cross-reactivity with keto and iminium substrates. In contrast to glucose dehydrogenase (GDH), neither PTDH nor ICDH showed any reactivity toward the tested substrates. Consequently, phosphite/PTDH and isocitrate/ICDH systems were employed for NADPH regeneration during the biocatalytic reduction of keto compounds. These systems thus present effective alternatives to glucose/GDH, offering a solution to eliminate unwanted cross-reactivity during enzymatic reductions.