A cold-active β-glucosidase (Bgl1C) from a sea bacteria Exiguobacterium oxidotolerans A011

Abstract

By constructing a genomic library, a new gene encoding β-glucosidase (Bgl1C) was cloned from Exiguobacterium oxidotolerans A011, which was isolated from deep sea mud. The putative β-glucosidase gene consisted of an open reading frame (ORF) of 1,347
nucleotides, and encoded a protein of 448 amino acids with a predicted molecular weight of 51.6kDa. Bgl1C belonged to the
glycoside hydrolase family 1, and the deduced amino acid sequence displayed the highest identity (68%) to the β-glucosidase
from Bacillus coahuilensis m4-4. Optimal conditions for activity were pH 7 and a temperature of 35°C and Bgl1C was stable in buffers ranging from pH
6.6 to 9. The specific activity, K
m, and V
max for the substrate p-nitrophenyl-β-d-glucopyranoside were 41Umg−1, 1.72mgml−1 and 0.45μgml−1s−1, respectively. Na+, Ca2+, EDTA and β-mercaptoethanol had no effect on the activity, while Hg2+, Cu2+, Co2+ strongly inhibited it. It is noteworthy that Bgl1C is a cold active enzyme that retains about 61% of its maximum activity
at 10°C. Structural model of Bgl1C revealed that some amino acids (glycine, alanine, serine, valine) concerned with plasticity
and flexibility were located around the active sites, this may contributed to the cold adaption of Bgl1C. These favorable
features make Bgl1C a potential candidate for various industrial applications.

Keywords
Exiguobacterium oxidotolerans A001-β-Glucosidase-Cold-active-Glycoside hydrolase family 1