earticle

영어

Ribose-5-phosphate isomerase (RpiB) from Clostridium thermocellum has been reported that converted d-psicose into d-allose as pharmaceutical compound without byproduct. Moreover, ribose-5-phosphate isomerase from Clostridium thermocellum has effective thermal stability among d-allose conversion enzymes.
A docking study of ribose-5-phosphate isomerase from Clostridium thermocellum with d-psicose in the real 3D structure was performed. The 11 active site residues, predicted according to a homology-based model, were separately replaced with Ala. The residue at position 132 was correlated with an increase in d-psicose isomerization activity. The R132E mutant showed the highest activity among mutants modified with Ala, Gln, Ile, Lys, Glu or Asp. The maximal activity of wild type and R132E mutant enzymes towards d-psicose was observed at pH 7.5 and 80°C. The thermal inactivation with half-lives of wild type enzyme was 15, 10, 6.6, 3.5, 1.2, and 0.5 h at 55, 60, 65, 70, 75, and 80°C, respectively. Whereas, that of R132E mutant enzymes was 21, 13, 8.3, 5.1, 2.6, and 0.8 h at 55, 60, 65, 70, 75, and 80°C, respectively. The specific activity and catalytic efficiency (kcat/Km) for d-psicose using the R132E mutant were 1.3- and 1.5-fold higher than those of the wild-type enzyme, respectively. The production rate of d-allose from d-psicose using the R132E mutant enzyme was higher than that using the wild-type enzyme.
After 80 min, the conversion yield of d-allose from d-psicose using the R132E mutant enzyme (32%) was 7% higher than that using the wild-type enzyme (25%).