Characterization of a novel l-amino acid oxidase with protein oxidizing activity from Penicillium steckii AIU 027

An enzyme exhibiting oxidase activity for β-lactoglobulin, myoglobin, and l-lysine-containing peptides was found from a newly isolated fungal strain, Penicillium steckii AIU 027. The enzyme also oxidized l-amino acids, Nα-benzyloxycarbonyl-l-lysine (Nα-Z-l-lysine) and Nε-Z-l-lysine, but not d-amino acids and amines. Thus, the enzyme was classified into a group of l-amino acid oxidases (l-AAOs). However, characteristics of this l-AAO were significantly different from those of other l-AAOs as follows. The l-AAO from P. steckii AIU 027 oxidized both the α-amino group and the ε-amino group in l-amino acids and l-lysine-containing peptides, and the Km values for l-lysine-containing polypeptides were lower than those for Nα-Z-l-lysine and l-lysine-containing dipeptides. The enzyme contained flavin and iron, and composed of four identical subunits with molecular mass of 75.3 kDa. The N-terminal amino acid sequence, ENIADVADAMGPWFDGVAYMKSKKN, was different from that of other l-AAOs. Thus, the l-AAO with protein oxidase activity was first reported here from P. steckii AIU 027.