Kinetics and thermodynamics for aldo/keto conversion of D‐xylose and D‐glucose catalyzed by xylose isomerase from Thermotoga naphthophilaRKU‐10

Abstract

BACKGROUND Aldo‐keto isomerizations of D‐xylose and D‐glucose catalyzed by xylose isomerase (XI) is commercially carried out to produce bio‐ethanol and high fructose corn syrup. XI is a metalloenzyme. In this paper, kinetics and thermodynamics of the activity and stability of hyperthermophilic recombinant XI from Thermotoga naphthophila RKU‐10T (TnapXI) were studied in the presence and absence of metal ions. RESULTS Kinetics parameters of recombinant XI from TnapXI were calculated as Km = 0.99 mmol L–1, Vmax = 500 μmol.mg−1.min−1, and kcat = 68.3 min−1 for the isomerization of D‐xylose(aldo)⇌D‐xylulose(keto), whereas for D‐glucose(aldo)⇌D‐fructose(keto) conversion Km = 7.72 mmol L–1, Vmax = 90 μmol.mg−1.min−1, and kcat = 12.4 min−1. Ionization constants were calculated as pKa1 = 6.0 and pKa2 = 7.6, whereas activation constants (Ka) of TnapXI were 0.3, 0.5, and 4.0 mmol L–1 for Co2+, Mn2+, and Mg2+, respectively. Inhibition constant (Ki) was 0.119 mmol L–1 for Ca2+. Q10 was 2.8 and Ea = 82.25 kJ.mol−1. Thermodynamics for isomerization were calculated as ∆H* = 79.2 kJ.mol−1, ∆G* = 83 kJ.mol−1, and ∆S* = −10.5 J.mol−1.K−1. The z‐value was 12.6 °C for apo‐TnapXI and 32.6 °C for holo‐TnapXI. Deactivation parameters were ∆G*(d) = 100 kJ.mol−1, ∆H*(d) = 206 kJ.mol−1, ∆S*(d) = 0.28 kJ.mol−1.K−1 for apo‐TnapXI and t1/2 = 18 min at 95 °C, while ∆G*(d) = 104 kJ.mol−1, ∆H*(d) = 767 kJ.mol−1, ∆S*(d) = 1.8 kJ.mol−1.K−1 for holo‐TnapXI and t1/2 = 65 min at 95 °C. CONCLUSION These noteworthy features make this enzyme an attractive candidate for the industrial production of fuel ethanol and high fructose corn syrup at high temperatures to maximize the product yield. © 2021 Society of Chemical Industry (SCI).

PbrbZIP15 promotes sugar accumulation in pear via activating the transcription of the glucose isomerase gene PbrXylA1

“…Based on transcriptome annotation, Pbr013598.1 (named as PbrSS1 ) encoded a starch synthase, possibly participating in starch biosynthesis (Nougué et al., 2014); Pbr002193.1 ( PbrXylA1 ) encoded a xylose isomerase, likely playing a role in glucose and xylose isomerization (Fatima et al., 2021); Pbr018465.1 ( PbrSOT19 ) and Pbr037514.1 ( PbrSOT21 ) encoded polyol transporters, which could be responsible for sorbitol transport (Gu et al., 2021); Pbr020127.1 ( PbrERDL6‐2 ) encoded an Early Response to Dehydration Like 6 (ERDL6) sugar transporter, potentially mediating glucose efflux from the vacuole into the cytosol (Zhu et al., 2021) (Figure S10; Table S4).…”

Enhanced High-Fructose Corn Syrup Production: Immobilizing Serratia marcescens Glucose Isomerase on MOF (Co)-525 Reduces Co2+ Dependency in Glucose Isomerization to Fructose

“…The production of HFCS hinges on glucose isomerase (GI), a catalyst converting D-glucose to D-fructose by isomerizing aldose to ketose [5,6]. In the enzymatic hydrolysis of starch for HFCS, the rate-limiting step is the glucose isomerization [7]. The isomerization reaction operates within a thermodynamic equilibrium, and elevated reaction temperatures enhance the conversion rate, underscoring the value of heat-resistant GIs for boosting HFCS yield [8,9].…”