Properties Of Acid Phosphatase From Wheat Germ

The biochemical properties of Acid Phospoatase (ACPase. E.C.3.1.3.2) from wheat germ was studied. The Michaelis-Menten constant (K_m) was 3.9×10^-4 mol/L with the p-Nitrophenyl phosphate (p-NPP) as substrate. The optimum pH value of the enzyme was 5.0 and the optimum temperature was 37℃. The enzyme was stable below 40℃. The relative enzyme activity only decreased 5.8% when temperature increased from 20℃ to 40℃, while rapidly decreased from 94.2% to 17.3% when temperature increased from 40℃ to 70℃.A survey of effect of metal ions on the ACPase from wheat germ showed that the activity of the enzyme was not significantly influenced by Mg²⁺, K⁺or Mn²⁺, was activated by Cr³⁺ and Co²⁺, was inhibited by Cu²⁺, Zn²⁺, Cd²⁺ and Ni²⁺. The inhibition of Zn²⁺ was demonstrated to be a noncompetitive inhibition by using Lineweaver-Burk method and K_i was 8 ×10^-6 mol/L determined by Dixon method. Study on the effects of Zn²⁺, Cu²⁺, Co²⁺ Cd²⁺ and Cr³⁺ on UV differential spectrum and fluorescent spectrum of the ACPase from wheat germ found: UV differential spectrum of the ACPase denatured respectively by these five metal ions showed absorption peaks appeared at 230nm. Co²⁺, Cu²⁺, Cr³⁺ and Zn²⁺ led to the red shift in UV differential absorption peak. The peaks of UV differential spectrum suggested that the conformation of enzyme molecule changed from ordered structure to random coils. The characteristic peak of the fluorescence emission of ACPase presented at 336 nm when the fluorescence excitation spectrum was at 278 nm.