Effect of divalent metals on phytase activity and enzymatic kinetics of As-hyperaccumulation ferns

Abstract

Phytase secreted by plant roots can hydrolyse phytate to provide phosphorus (P) for plants growth. To ensure the plant growth and to reduce the pollution caused by heavy metal in environment, this paper studies the phytase activity in environment. The activity of phytase in the environment is directly related to the bioavailability of phytate. The catalytic reaction between phytase and phytate is affected by divalent metal ions in the environment, due to Zn2+, Cu2+, Fe2+ and Ca2+ can easy to form a stable chelate with phytate. Through the enzymatic kinetic equations, Zn2+ and Ca2+ can cause conformational changes of enzyme molecules, resulting in catalytic function loss, and partial competition between Cu2+/Fe2+ and substrates can affect the catalytic efficiency of phytase. The results showed that the effects of different divalent metal ions on phytase activity were Zn2+ > Cu2+ > Fe2+ > Ca2+. The phytase activity showed twice-inhibition after interacting others divalent metal ions with Ca2+ and existed the enlarge inhibition effect between Zn2+/Cu2+ and Ca2+, but there was an antagonistic effect between Fe2+ and Ca2+, which may be related to the replacement ability between different divalent metal ions and the ability of binding phytase.

Keywords

• phytase
• divalent metal ion
• enzymatic kinetics
• arsenic hyperaccumulation ferns