Study On Artificial Hydrolase Based On Peptides And Multiwalled Carbon Nanotube Conjugations

The vast majority of natural enzymes are proteins that have the function of biological catalysis, which take part in almost all of the cellular activities. Different from other non-biological catalysts, the enzymes have outstanding catalytic activities, high substratespecificities and mild reaction conditions and so on. But the enzyme is easily affected by various environmental factors and inactivated, for example poor tolerance and high production cost limits its application in industry and life. As a replacement of natural enzyme, mimic enzyme is effective and there is a broader range of application.Hydrolase was chosen as an object of enzyme mimic system, using p-nitrophenylacetate (PNPA) as the reaction substrate and the optimization of mimic enzyme was obtained by investing the effects of different conditions. Natural hydrolytic enzymes generally contain catalytic groups (the catalytic triad) that directly involve in the catalytic process and connecting groups that involve in substrate binding. By assembling polypeptides (SHELKLKLKL as catalytic center and WLKLKLKL as connected center)onto carbon nanotubes, the optimized CNT-(SHE/W)2:1-LKLKLKL was obtained with SHELKLKLKL of 67.7% and WLKLKLKL of 32.3%. The experiments indicated that the catalytic triad toward the surface of carbon nanotube had a higher activity than toward the solution, suggesting that carbon nanotube not only served as a platform for attaching active amino acids, but also created a hydrophobic microenvironment and facilitated the proton transfer process to enhance the catalytic activity. The artificial enzyme exhibited Michaelis-Menten behaviour, indicating that it was indeed a mimic of the corresponding natural enzyme. After taking into consideration several aspects, it was showed that the C.NT-(SHE/W)2:1-LKLKLKL had the highest catalytic activity to hydrolyse PNPA, and its Km and Kcat/Km was 1.66 mM, 0.62 M-1S-1, respectively.This work showed that a well-designed combination of CNT and short peptides containing active sites can mimic a natural enzyme. This study is expected to provide some guidance and help for the study of artificial enzyme.