ABSTRACT
The phosphotriesterase (PTE) (EC 3.1.8.1) is a member of the amidohydrolase superfamily (Holm and Sander 1997). Like other members of this superfamily PTE utilizes one or two divalent metal ions to activate a hydrolytic water molecule for a nucleophilic attack at tetrahedral phosphorus or trigonal carbon centres. The active site of the native enzyme contains two zinc ions per monomer. The enzyme retains catalytic activity when the native Zn2+ is replaced by Co2+, Cd2+, Ni2+, or Mn2+. The cobalt-substituted enzyme is the most active form (Omburo et al. 1992).
