Purification and characterization of a novel acid-tolerant and heterodimeric β-glucosidase from pumpkin (Cucurbita moschata) seed

A novel beta-glucosidase was purified from pumpkin (Cucurbita moschata) seed by anion exchange chromatography and gel permeation chromatography, and its molecular mass was determined to be 42.8 kDa by gel permeation chromatography. The heterodimeric structure consisting of two subunits, free from disulfide bonds, was determined by nativePAGE analysis followed by zymography. The enzyme was maximally active at pH 4.0 and 70 degrees C, and V-max, K (m), and kcat values were 0.078 units mgL(-1) protein, 2.22 mM, and 13.29 minL(-1), respectively, employing p-nitrophenyl-beta-D-glucopyranoside as the substrate. The high content of glycine determined by amino acid analysis implies that the enzyme possesses flexible conformations and interacts with cell membranes and walls in nature. Circular dichroism studies revealed that the high stability of the enzyme within the pH range of 2.0e10.0 is due to its reversible pH-responsive characteristics for alpha-helixeantiparallel beta-sheet interconversion. (C) 2021, The Society for Biotechnology, Japan. All rights reserved.