Enhanced Stabilization Effect of Cofactor Thiamine Pyrophosphate in the Covalent Immobilization of Formolase

Formolase, a thiamine pyrophosphate (TPP)-dependent enzyme, catalyzes the carboligation of three one-carbon formaldehyde molecules into one three-carbon dihydroxyacetone molecule. It has many important functions in the biosynthesis of carbon-based compounds and utilization of CO2. However, the enzyme has low activity and stability in the catalytic process, resulting in high cost in the applications. To improve the stability, formolase was immobilized onto magnetic nanoparticles, which were designed to have functional epoxy groups for covalently binding the enzyme. In the immobilization, effects of pH, temperature, and cofactor TPP on the immobilization were investigated and optimized. The results showed that the retention activity of immobilized formolase was highly related to TPP. In the presence of TPP, the specific activity of the immobilized formolase was 6.8 times higher than that without TPP. The optimal immobilization conditions were as follows: a temperature of 20 °C, a pH of 7.0, an immobilization time of 8 h, and an enzyme loading of 20 mg/g. Molecular docking was used to analyze the effect of TPP on the stabilization of the enzyme in the immobilization, which indicated that TTP could stabilize the enzyme structure during the immobilization. The stabilization effect of TPP could be a reference in the immobilization of other enzymes with TPP as the cofactor.