Construction Of A Novel Nucleotide-based Coordination Polymer Immobilized Enzyme

Enzyme is an efficient green catalyst,but its vulnerability and difficulties of separation from products limited the application in industry.These problems can be solved by enzyme immobilization,but different enzyme has different properties and reaction conditions,so it is significant to find suitable methods and materials for enzyme immobilization.Metal nucleotides coordination polymers(MNCPs)with high biocompatibility and nontoxic can immobilize the enzyme by self-assembly and the process is simple and the conditions are mild.MNCPs not only can protect enzymes,but also MNCPs with activity of natural enzyme can catalyze the reaction instead of natural enzymes.In this paper,acid stable Zr based MNCPs and Cu based MNCPs with NAD(P)H oxidase activity were constructed to immobilize the enzyme.In this paper,Zr4+/AMP with high acid stability was synthesized by self-assembly of zirconium ion and Adenosine 5'-monophosphate disodium salt(AMP).The higher valence Zr4+have more holes,which could enhance the electrostatic interaction between metal ions and nucleotides and had more advantages when competing with hydrogen ions,so the Zr4+/AMP exhibited high acid stability.After incubation in the solution of pH=3 for 1 h,Zr4+/AMP still remained a clear round particle structure,and the leaching rate of BSA in Zr4+/AMP was only 11%.The Zr4+/AMP was used to immobilize acidophilic chloroperoxidase(CPO)and ?-galactosidase(?-gal).It was found that the catalytic activity of the immobilized enzymes was significantly improved due to the affinity of Zr4+to natural enzymes and higher substrate concentration.The immobilized enzymes also exhibited high stability and reusability.Copper based MNCPs(Cu2+/AMP and Cu2+/GMP)with NAD(P)H oxidase activity was constructed by self-assembly of copper ions and nucleotides.The high oxidation activity of Cu2+/AMP and Cu2+/GMP mainly attribute to the active center of Cu2+.Cu2+/AMP and Cu2+/GMP with high catalytic activity showed high reusability.After 11 cycles,the Cu2+/AMP and Cu2+/GMP remained more than 60%of the initial activity when catalyzing the oxidation of NADH.After 9 cycles,the Cu2+/AMP remained more than 95%of the initial activity when catalyzing the oxidation of NADPH.Cu2+/AMP with NADH oxidase activity was combined with NAD+dependent alcohol dehydrogenase(ADH)to construct a multi-enzyme system with recycling cofactor.In this system,ADH exhibited high activity due to the increase of substrate concentration and the inhibition of the diffusion of intermediate products.Besides,the immobilized ADH also showed high stability and reusability.After 8 cycles,the immobilized ADH remained more than 57%of the initial activity.