Recombinant expression of an l-amino acid oxidase from the fungus Hebeloma cylindrosporum in Pichia pastoris including fermentation

Abstract

l-amino acid oxidases (LAAOs) are flavoenzymes that catalyze the oxidative deamination of l-amino acids to the corresponding α-keto acids, ammonia, and hydrogen peroxide. Here, we show the overexpression, purification, and the characterization of LAAO4 from the fungus Hebeloma cylindrosporum in the yeast Pichia pastoris with a 9His-tag and compare this with the recently characterized 6His-hcLAAO4 expressed in E. coli. The expression of the enzyme with an ER-signal sequence in P. pastoris resulted in a glycosylated, secreted protein. The enzymatic activity without activation was higher after expression in P. pastoris compared to E. coli. Due to treatment with acidic pH, a striking increase of activity could be detected for both expression systems resulting in similar specific activities after acid activation. Regarding the substrate spectrum, temperature stability, K_m, and v_max values, hcLAAO4 showed very few differences when produced in these two expression systems. A higher yield of hcLAAO4 could be obtained by fermentation.