Enzymatic direct carboxylation under supercritical CO2

Substrate Promiscuity of Thermoplasma acidophilum Malic Enzyme for CO2 Fixation Reaction

“…This addition led to a substantial improvement, with the yield increasing to 67%, an 18-fold increase (Figure a). This result indicated that the Ta GDH reaction enhanced the thermodynamic feasibility of the carboxylation reaction, aside from cofactor regeneration, as expected from the case using Ta IDH and Ta GDH …”

“…Since the hydrophilic amino acid residues such as Asn304 and Thr46* of Ta ME were suggested to be important in determining substrate specificity, it is expected that introducing site-directed mutations in these residues will further expand the substrate specificity in the future studies. Additionally, Ta ME may potentially catalyze the selective synthesis of ( S )-hydroxy acids, which could be complementary to our previously developed carboxylation reaction with Ta IDH …”

“…This result indicated that the TaGDH reaction enhanced the thermodynamic feasibility of the carboxylation reaction, aside from cofactor regeneration, as expected from the case using TaIDH and TaGDH. 18 Then, we investigated the reaction conditions for the reductive carboxylation of 1a by TaME, gaseous CO 2 and TaGDH. The effects of pH, divalent metal ion, substrate concentration, and CO 2 pressure on the carboxylation reaction were investigated.…”

“…The absolute configuration of the product 2b, which will be determined in the future study, may be L-(S), the opposite enantiomer of what is produced by the carboxylation using TaIDH. 18 This is because TaME, belonging to the "malic enzymes" family, accepts (S)-hydroxy acids as substrates, while IDH, belonging to the "β-decarboxylating dehydrogenases" family, accepts (R)-hydroxy acids as substrates. 35 It is noteworthy that TaME was found to exhibit the substrate promiscuity for both decarboxylation and carboxylation in this study, as it belongs to the "malic enzymes" family.…”

Immobilization of Baeyer–Villiger monooxygenase from acetone grown Fusarium sp.

“…FBVMO nanocrystal solution (1 mL) prepared from 1 U of free FBVMO, heat treated Thermoplasma acidophilum glucose dehydrogenase solution (1 mL, 1.95 U) prepared as reported previously (Are et al 2021), cyclohexanone solution dissolving 100 mg of cyclohexane in 1 mL of aqueous solution containing 10% of diethylene glycol, NADPH (50 mg), glucose solution (1 mL of 1 M solution), and sodium phosphate buffer (17 mL, 50 mM, pH 8.0) were mixed and incubated at 40 ˚C at 150 rpm for 3 days. The reaction was repeated 5 times to convert 500 mg (5.09 mmol) of cyclohexanone in total.…”