Comparative Studies on the Interaction of Proteinase-K with Fe2O3, Fe3O4 and SiO2 Nanoparticles

The interaction of Fe2O3, Fe3O4 and SiO2 nanoparticles with proteinase K activity was investigated using UV–vis spectroscopy. Proteinase K EC (3.4.21.14) is a member of serine protease family, which is produced from fungus Tritirachum album Limber. The effects of nanoparticles on proteinase K activity were studies at 40˚C in pH 7.0 using sodium phosphate as buffer. It was found that in the presence of nano-Fe2O3 and nano-Fe3O4, Vmax was decreased but Km was constant. This results indicated that nano-Fe2O3 and nano-Fe3O4 acted as noncompetitive inhibitors. In the presence of nano-SiO2 the amount of Km increased but Vmax decreased, that showed nano-SiO2 acted as a mixed inhibitor. The dissociation constant (Ki) value for binding nano-Fe2O3, nano-Fe3O4 to proteinase K was equal to 11μM and 8.5μM respectively that indicated the binding of nano-Fe3O4 to the enzyme was stronger than nano-Fe2O3. The KI and Ki value for nano-SiO2 was 22.5μM and 8μM respectively.