Self-assembly of metal-cholesterol oxidase hybrid nanostructures and application in bioconversion of steroids derivatives

A cholesterol oxidase (COD) was hybridized with Ca2+,Zn2+,Al3+,Fe2+ and Mn2+. After precipitation with PO43- at 4 degrees C for 72 h, the resulting pellets were freeze-dried. In scanning electron microscopy assays, the metal-COD complexes revealed flower-like or granular structures after hybridization. Fourier transform infrared spectroscopy assay revealed the characteristic peaks of both the enzyme and metal materials. X-ray diffraction analysis indicated that COD was encapsulated in CaHPO4 center dot 2H(2)O-, Zn-3(PO4)(2)center dot 4H(2)O-, AlPO4-, FeP4- and Mn-3(PO4)(2)center dot 3H(2)O-based nanostructures, respectively. Differential scanning calorimetry assay indicated significant increases in thermo-denaturation temperatures from 60.5 degrees C to 167.02 degrees C, 167.02 degrees C, 137.70 degrees C, 172.85 degrees C and 160.99 degrees C, respectively. Using steroid derivatives as substrates, this enzyme could convert cholesterol, pregnenolone, dehydroepiandrosterone, ergosterol, beta-sitosterol and stigmasterol to related single products. Hybridization in metal-based nanostructures could significantly enhance the initial conversion ratio and reaction stability of the enzyme. In addition, substrate selectivity could be affected by various metal materials. Briefly, using Ca2-,Zn2+, Al3-, Fe2+ and Mn2+ as hybrid raw materials could help to encapsulate COD in related metal-enzyme nanostructures, and could help to promote the stability and tolerant properties of the enzyme, while also enhancing its catalytic characteristics.