Aspergillus fumigatus L-Amino Acid Oxidase-Two Step Purification and Characterization of the Enzyme

Abstract

L-amino acid oxidase (L-aao) obtained from Aspergillus fumigatus was purified by ion exchange and gel filtration chromatographies. The yield of L-aao in the ion- exchange chromatography was 24.40 % while the recovery of purified L-aao by gel filtration was 18.70 % of the crude enzyme. The molecular mass of the purified enzyme was estimated to be 55 kDa by SDS PAGE and 93 kDa by gel filtration. The enzyme was stable up to 40oC and over a broad pH range of 5.6-9.2. The enzyme has higher specificity towards hydrophobic aromatic L-amino acids namely tyrosine and phenylalanine. The kinetic parameters, Km and Vmax were determined as 43.47 mM and 0.0434 μmol/ min/mL respectively. Ten mM Benzoic acid and EDTA completely inhibited the enzyme, while minimum inhibition with glycine (29.56%) and α-napthol (12.4%) were observed. Riboflavin, sodium azide and 8-hydroxyquinoline inhibit the enzyme up to 44.89%, 49.63% and 70.07% respectively. MgSO4 at 10-4 M and 10-3 M increased the enzyme activity by 1.72 and 2.22 fold respectively, while CuSO4 at 10-3 M increased the activity by 1.65 fold. This is the first report of purification of L-aao from Aspergillus fumigatus.