Purification and characterization of a β-N-acetylhexosaminidase from wheat bran and its applicability to biocontrol of Fusarium solani

Abstract

N-acetyl-β-d-hexosaminidase was purified from wheat bran and characterized. The purified enzyme showed two protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with molecular mass of 75 and 78 kDa. The enzyme exhibited optimum pH and temperature at 5.0 and 50°C, respectively. The enzyme was active on the substrates of p-nitrophenyl-N-acetyl-β-d-glucosaminide (pNP-GlcNAc) and p-nitrophenyl-N-acetyl-β-d-galactosaminide (pNP-GalNAc), whereas inactive on pNP-β-d-glucopyranoside, pNP-β-d-galactopyranoside, swollen chitin, and colloidal chitin, suggesting high substrate specificity. The enzyme activity for pNP-GlcNAc was stable at pH 3–6 and under 50°C. The K_m, V_max and K_cat for pNP-GlcNAc were 0.014 mM, 0.05 μmol/min, and 3.01×10⁶ min⁻¹, respectively. The enzyme could be completely inhibited at 1–10 mM HgCl₂ and AgNO₃, suggesting that the intact thiol group is essential for activity. β-N-Acetylhexosaminidase from wheat bran could inhibit the conidial germination and digest the hyphae of Fusarium solani.