Mutated PTE enzyme derived from parathion hydrolase having sequence SEQ ID NO: 1, and containing the following mutations with respect to sequence SEQ ID NO: 1: - Substitution of threonine T by proline P, in position 13, - Substitution of isoleucine I by valine V, in position 14, - Substitution of alanine A by serine S, in position 60, - Substitution of serine S by arginine R, in position 79, - Substitution of tyrosine Y by histidine H, in position 124, - Substitution of isoleucine I by valine V, in position 218, - Substitution of histidine H by tyrosine Y, in position 225, - Substitution of glutamine Q by arginine R, in position 258, - Substitution of leucine L by threonine T, in position 271, said mutated PTE enzyme having sequence SEQ ID NO: 3, or containing the following mutations with respect to sequence SEQ ID NO: 1: - Substitution of threonine T by proline P, in position 13, - Substitution of isoleucine I by valine V, in position 14, - Substitution of alanine A by serine S, in position 60, - Substitution of isoleucine I by cysteine C in position 74 - Substitution of serine S by arginine R, in position 79, - Substitution of phenylalanine F by valine V, in position 100, - Substitution of tyrosine Y by histidine H, in position 124, - Substitution of isoleucine I by valine V, in position 218, - Substitution of histidine H by glutamine Q, in position 222, - Substitution of histidine H by tyrosine Y, in position 225, - Substitution of alanine A by valine V, in position 238, - Substitution of leucine L by methionine M, in position 240, - Substitution of isoleucine I by asparagine N, in position 242, - Substitution of glutamine Q by arginine R, in position 258, - Substitution of serine S by leucine L, in position 276, said mutated PTE enzyme having sequence SEQ ID NO: 4. - Substitution of threonine T by proline P, in position 13, - Substitution of isoleucine I by valine V, in position 14, - Substitution of alanine A by serine S, in position 60, - Substitution of serine S by arginine R, in position 79, - Substitution of tyrosine Y by histidine H, in position 124, - Substitution of isoleucine I by valine V, in position 218, - Substitution of histidine H by tyrosine Y, in position 225, - Substitution of glutamine Q by arginine R, in position 258, - Substitution of leucine L by threonine T, in position 271, said mutated PTE enzyme having sequence SEQ ID NO: 3, or containing the following mutations with respect to sequence SEQ ID NO: 1: - Substitution of threonine T by proline P, in position 13, - Substitution of isoleucine I by valine V, in position 14, - Substitution of alanine A by serine S, in position 60, - Substitution of isoleucine I by cysteine C in position 74 - Substitution of serine S by arginine R, in position 79, - Substitution of phenylalanine F by valine V, in position 100, - Substitution of tyrosine Y by histidine H, in position 124, - Substitution of isoleucine I by valine V, in position 218, - Substitution of histidine H by glutamine Q, in position 222, - Substitution of histidine H by tyrosine Y, in position 225, - Substitution of alanine A by valine V, in position 238, - Substitution of leucine L by methionine M, in position 240, - Substitution of isoleucine I by asparagine N, in position 242, - Substitution of glutamine Q by arginine R, in position 258, - Substitution of serine S by leucine L, in position 276, - Substitution of threonine T by proline P, in position 13, - Substitution of isoleucine I by valine V, in position 14, - Substitution of alanine A by serine S, in position 60, - Substitution of isoleucine I by cysteine C in position 74 - Substitution of serine S by arginine R, in position 79, - Substitution of phenylalanine F by valine V, in position 100, - Substitution of tyrosine Y by histidine H, in position 124, - Substitution of isoleucine I by valine V, in position 218, - Substitution of histidine H by glutamine Q, in position 222, - Substitution of histidine H by tyrosine Y, in position 225, - Substitution of alanine A by valine V, in position 238, - Substitution of leucine L by methionine M, in position 240, - Substitution of isoleucine I by asparagine N, in position 242, - Substitution of glutamine Q by arginine R, in position 258, - Substitution of serine S by leucine L, in position 276, said mutated PTE enzyme having sequence SEQ ID NO: 4.