Amino acid-mediated aldolase immobilisation for enhanced catalysis and thermostability

To improve the properties of the immobilised 2-deoxy-d-ribose-5-phosphate aldolase (DERA), unreacted functional groups on support surface were blocked with amino acids. The relative activities of the immobilised enzyme were 144.7 and 141.9% when the post-immobilisation modification was done with Arg and Phe, respectively. The residual activity of immobilised DERA after heating at 60 °C for 120 min was 65.1% when Phe and Val were used as the blocking amino acids, a 2.0- and 2.87-fold increase over that of the immobilised (no post-immobilisation blocking) and free DERA. Immobilised DERA maintained maximal activity in 2-deoxyribose-5-phosphate (DR5P) synthesis up to 600 mM of acetaldehyde, which was much higher than the amount of acetaldehyde tolerated by free enzyme (300 mM). This superior resistance to high acetaldehyde concentrations would accelerate the DR5P reaction by shifting the reaction equilibrium towards the product. The results from this study suggest that the novel immobilised DERA may be useful for industrial applications.