N-linked glycosylation affects catalytic parameters and fluctuation of the active center of Aspergillus awamori exo-inulinase

Abstract

Heterogeneous expression of enzymes allows large-scale production with reduced costs. Changes in glycosylation often occur due to changes in the expression host. In the study, the catalytic and biochemical properties of Aspergillus awamori exo-inulinase 1 are compared for A. awamori and Penicillium verruculosum expression hosts. The tertiary structure contains seven sites of N-glycosylation, with two of them located near the active center. If expressed in P. verruculosum, the enzyme was four times less glycosylated and two times more active toward sucrose, raffinose, and stachyose due to an increase in k_cat. These substrates with a short chain of 2–4 monosaccharide units were used to characterize the interaction of the substrate with the amino acid residues in the active center while preventing the interaction of the substrate with N-linked glycans. Molecular dynamics simulations showed an increase in the fluctuation of the active center with an increase in the length of N-linked glycans. The fluctuation of the residues N40 and Q57, which interact with the hydroxyl group O5 of the fructose unit in the −1 subsite of the active center, was increased by 1.6 times. The fluctuation of the residue W335, which interacts with the hydroxyl group O1 of the fructose unit together with the catalytic residue D41 and affects the torsion angle geometry of the substrate molecules, was increased by 1.5 times. The residue R188, which analogously to W335 affects the torsion angle geometry of the substrate molecules, was also among the affected residues with a 1.2-fold increase in the fluctuation.