Characterization and catalytic kinetics studies of N-cetyl-O-sulfate chitosan multinuclear copper complex as an artificial hydrolase

A novel multinuclear Cu(II) complex of N-cetyl-O-sulfate-chitosan (NCOS) was prepared and structurally characterized by X-ray photoelectron spectroscopy (XPS) and Infrared radiation (IR) spectroscopy. The capability of chelated copper ions to coordinate with the novel ligand was improved 55% over native chitosan. As artificial multinuclear phosphodiesterase, NCOS-Cu(II) complex was adopted to study its catalytic kinetics on hydrolysis of bis(4-nitriphenyl)phosphate (BNPP) in the heterogeneous system. The initial rate of BNPP hydrolysis catalyzed by NCOS-Cu(II) was 7 × 10⁴ times higher than that of spontaneous BNPP hydrolysis. The behavior of BNPP catalytic hydrolysis fits Michaelis-Menten kinetics with k_cat of 2.3 × 10^-5 s^-1, the maximum velocity (V_max) of 2.3 × 10^-9 mol L^-1 s^-1 and the Michaelis constant (K_M) of 2.9 × 10^-4 M, respectively. The metal-hydroxyl catalytic mechanism has been proposed.