Details

Autor(en) / Beteiligte

• Geiger, Gabriella
• Furrer, Gerhard
• Funk, Felix
• Brandl, Helmut
• Schulin, Rainer

Titel

Heavy Metal Effects on β-Glucosidase Activity Influenced by pH and Buffer Systems

Ist Teil von

• Journal of enzyme inhibition, 1999, Vol.14 (5), p.365-379

Ort / Verlag

Switzerland: Informa UK Ltd

Erscheinungsjahr

1999

Link zum Volltext

Quelle

EZB-FREE-00999 freely available EZB journals

Beschreibungen/Notizen

• Abstract Inhibition of β-glucosidase activity by Cu(II), Zn(II) and Ni(II) was investigated as a function of pH and buffer type. Both factors were found to exert a strong effect on the activity of the enzyme. All three of the investigated heavy metals inhibited the enzyme activity in acetate buffer. At metal concentrations of 0.6 mM, Zn and Ni reduced the enzyme activity by 25-30% under optimal pH conditions (pH 5-5.2). Under the same conditions, Cu showed an even more pronounced inhibitory effect than Zn and Ni. In presence of 0.6 mM Cu, the enzyme activity was lowered by more than 90% in comparison to metal free systems. In contrast to these results, no enzyme inhibition was observed in citrate buffer, even in the presence of 1 mM Cu. The inhibition of β-glucosidase activity by Cu increased with increasing pH. Inhibition by Zn and Ni was less pH-dependent in the observed pH range (pH 4-5.5). Copper caused a distinct shift in the pH optimum of enzyme activity, whereas this was not the case for Zn or Ni. The effects of buffer and pH on enzyme inhibition by Cu, Zn and Ni were successfully described using a chemical speciation model, based on the assumption that enzyme activity depends on the protonation of the amino acids at the reactive site and that enzyme activity is inhibited by complexation of the reactive sites by the heavy metal cations. The results show the importance of taking chemical conditions and speciation into account when investigating the effect of heavy metal cations on biological systems.