Acta Phys. -Chim. Sin. ›› 2000, Vol. 16 ›› Issue (08): 764-768.doi: 10.3866/PKU.WHXB20000818

• Note • Previous Articles    

Microcalorimetry Study on the Reaction of Metallothionein with Cd2+ and Pb2+

Huan Yu, Chu De-Ying, Tang Yong, Cao Wei   

  1. College of Chemistry and Molecular Engineering,Peking University,Beijing 100871
  • Received:1999-12-17 Revised:2000-03-24 Published:2000-08-15
  • Contact: Chu De-Ying


Metallothionein, a class of low molecular weight, metal- and cysteine-rich Proteins, are postulated to play a central role in metal-related biological processes such as the detoxification of Cd2+and Pb2+. The thermal Properties of the interactions of rabbit liver Zn_7MT2 and apo-MT2 with Cd2+ and Pb2+ were studied using isothermal titration calorimeter. The same product Cd_7MT formed in the reactions of Cd2+ with Zn_7MT2 and apo-MT2, while the reactions of Ph2+ with Zn_7MT2 and apo-MT2 Produced two MT species Ph_7MT and Ph_7MT'. The thermodynamic parameters (△H、 △G、 △S, etc. ) for the reactions of MT with 1 mol metal ions were measured at 293.15 K, pH 4.70. All of these reactions are spontaneous, exothermic processes. The values of △G and K show that Cd2+ is more affinitive to MT than Ph2+. The equilibrium constants K of the replacement reactions of Zn_7MT2 by 1 mol Cd2+ and Pb2+ are 2. 7×105 and 1. 3×105 respectively, that means the concentrations of free Cd2+ and Pb2+ are depressed to about 1. 0×10-5 after the reactions with Zn_7MT2. These data can be used to evaluate quantitatively the ability of MT in Cd2+ and Pb2+ detoxificatio.

Key words: Metallothionein, Cadmium(II) ion, Lead(II) ion, Isothermal titration calorimetry