Functional classification of esterases from leaves of Aspidosperma polyneuron M. Arg. (Apocynaceae)

Abstract

Polyacrylamide gel electrophoresis system (PAGE) and inhibition tests for biochemical characterization of α- and β-esterases were used to obtain a functional classification of esterases from Aspidosperma polyneuron. The characterization of α and β-esterases from young leaves of A. polyneuron by the PAGE system showed fourteen esterase isozymes. The differential staining pattern showed that Est-2 isozyme hydrolyzes β-naphthyl acetate; Est-6, Est-7 and Est-8 isozymes hydrolyze α-naphthyl acetate, and Est-1, Est-3, Est-4, Est-5, Est-9, Est-10, Est-11, Est-12, Est-13, and Est-14 isozymes hydrolyze both α- and β-naphthyl acetate. Inhibition pattern of α- and β-esterases showed that Folidol is a more potent inhibitor that Malathion, while Thiamethoxan (an insecticide with organophosphorus-like action) acts as an Est-4 and Est-6 inhibitor and induces the appearance of Est-5 and Est-7 isozymes as more intensely stained bands. Inhibition tests showed that OPC insecticides inhibit or activate plant esterases. Thus, plant esterases may be used as bioindicators to detect the presence and toxicity of residues of topically applied insecticides in agriculture and may be valuable for monitoring pollutants in the environment.