Interaction Between Nanoparticulate Anatase TiO2 and Lactate Dehydrogenase

In order to study the mechanisms underlying the effects of TiO2 nanoparticles on lactate dehydrogenase (LDH, EC1.1.1.27), Institute of Cancer Research region mice were injected with nanoparticulate anatase TiO2 (5 nm) of various doses into the abdominal cavity daily for 14 days. We then examined LDH activity in vivo and in vitro and direct evident for interaction between nanoparticulate anatase TiO2 and LDH using spectral methods. The results showed that nanoparticulate anatase TiO2 could significantly activate LDH in vivo and in vitro; the kinetics constant (Km) and Vmax were 0.006 mu M and 1,149 unit mg(-1) protein min(-1), respectively, at a low concentration of nanoparticulate anatase TiO2, and 3.45 and 0.031 mu M and 221 unit mg(-1) protein min(-1), respectively, at a high concentration of nanoparticulate anatase TiO2. By fluorescence spectral assays, the nanoparticulate anatase TiO2 was determined to be directly bound to LDH, and the binding constants of the binding site were 1.77 x 10(8) L mol(-1) and 2.15 x 10(7) L mol(-1), respectively, and the binding distance between nanoparticulate anatase TiO2 and the Trp residue of LDH was 4.18 nm, and nanoparticulate anatase TiO2 induced the protein unfolding. It was concluded that the binding of nanoparticulate anatase TiO2 altered LDH structure and function.