Purification and characterization of amine oxidase from Vigna mungo L. seedlings

Abstract

Amine oxidases (AO) are a group of enzymes that catalyze oxidative deamination of various amines and thus are of potential use in analytical applications. Amine oxidase from five-day-old Vigna mungo L. seedlings (VAO) was purified using ammonium sulfate fractionation and Q-Sepharose chromatography to 544 purification folds with 65% yield. VAO apparently is a homodimer with denatured molecular weight of 73 kDa. This enzyme is relatively stable in a pH range of 6.0 to 8.0 and at temperature below 40°C with a complete activity loss upon storage at pH 4.0 or temperature over 60°C (1 h). Kinetics studies of VAO with putrescine, cadaverine, histamine, and tyramine showed k_cat/K_m values of 2.54×10⁷, 6.73×10⁶, 2.65×10⁵, and 3.31×10³ M^–1 s^–1, respectively, with undetectable catalytic activity toward tryptamine. VAO was partially inhibited by ethylenediaminetetraacetic acid (EDTA) and completely inhibited by phenylhydrazine, suggesting it is likely a member of copper-containing AO family.

Key words: Amine oxidase, cadaverine, histamine, putrescine, tyramine, tryptamine, Vigna mungo L.