Continuous Reusability using Immobilized HasApf in Chemoenzymatic Deracemization: A New Heterogeneous Enzyme Catalysis.

This study found that the calibration curve of heme acquisition system A (HasA, a new reactive active species) immobilized by a porous ceramic particle (ImHApf; immobilized HasA from Pseudomonas fluorescens ) can be constructed in the range of 1750-1450 cm-1 using Fourier transform infrared spectroscopy (FTIR) analysis, and evaluated its catalytic efficiency. In the asymmetric oxidation of rac -1-(6-methoxynaphthalen-2-yl)ethanol ( rac - 1 : a naproxen precursor), a product ketone from the ( R )-isomer is desymmetrized using NaBH₄ and continuously reused even if treated with an organic solvent in 50 mM glycine-NaOH buffer at 40 °C in the absence of nicotinamide adenine dinucleotide (NAD(P)), leading to >99% enantiomeric excess and >90% chemical yield; the activity was calculated at 0.74 ± 0.03 mU/(mg·min) and the turnover number was determined to be approximately 2 × 10⁶. It was confirmed that the other sec -alcohols such as rac -1-(2-naphthyl)ethanol ( rac - 2 ) and m - and p -substituted rac -1-phenyl ethanols ( rac - 3ab - 6ab ) using ImHApf can also yield a single stereoisomer from a racemate. Therefore, HasA immobilization can be expected to become an important tool for building an environmentally friendly system that promotes industrial sustainability.