Expression and characterization of a glucose-tolerant β-1,4-glucosidase with wide substrate specificity from Cytophaga hutchinsonii.
Cytophaga hutchinsonii is a gram-negative bacterium that can efficiently degrade crystalline cellulose by a novel strategy without cell-free cellulases or cellulosomes. Genomic analysis implied that C. hutchinsonii had endoglucanases and β-glucosidases but no exoglucanases which could processively digest cellulose and produce cellobiose. In this study, BglA was functionally expressed in Escherichia coli and found to be a β-glucosidase with wide substrate specificity. It can hydrolyze pNPG, pNPC, cellobiose, and cellodextrins. Moreover, unlike most β-glucosidases whose activity greatly decreases with increasing length of the substrate chains, BglA has similar activity on cellobiose and larger cellodextrins. The Kmvalues of BglA on cellobiose, cellotriose, and cellotetraose were calculated to be 4.8 × 10-2, 5.6 × 10-2, and 5.3 × 10-2mol/l, respectively. These properties give BglA a great advantage to cooperate with endoglucanases in C. hutchinsonii in cellulose degradation. We proposed that C. hutchinsonii could utilize a simple cellulase system which consists of endoglucanases and β-glucosidases to completely digest amorphous cellulose into glucose. Moreover, BglA was also found to be highly tolerant to glucose as it retained 40 % activity when the concentration of glucose was 100 times higher than that of the substrate, showing potential application in the bioenergy industry.
State Key Laboratory of Microbial Technology, College of Life Science, Shandong University, Jinan, 250100, China.|Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen, 361005, China.
Cong
C
Zhang
State Key Laboratory of Microbial Technology, College of Life Science, Shandong University, Jinan, 250100, China.
Xifeng
X
Wang
State Key Laboratory of Microbial Technology, College of Life Science, Shandong University, Jinan, 250100, China.
Weican
W
Zhang
State Key Laboratory of Microbial Technology, College of Life Science, Shandong University, Jinan, 250100, China.
Yue
Y
Zhao
State Key Laboratory of Microbial Technology, College of Life Science, Shandong University, Jinan, 250100, China. luxuemei@sdu.edu.cn.
Xuemei
X
Lu
D002475:Cellobiose / Q000096:biosynthesis; D002482:Cellulose / Q000031:analogs & derivatives / Q000378:metabolism*; D003589:Cytophaga / Q000201:enzymology* / Q000378:metabolism; D003912:Dextrins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D015202:Protein Engineering; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D013780:Tetroses / Q000378:metabolism; D001617:beta-Glucosidase / Q000235:genetics* / Q000378:metabolism*
D003912:Dextrins; D011994:Recombinant Proteins; D013780:Tetroses; D002475:Cellobiose; C048468:cellotetraose; D002482:Cellulose; C068994:cellodextrin; D001617:beta-Glucosidase; D005947:Glucose
Cytophaga hutchinsonii; Glucose-tolerant; Synergy; Wide substrate specificity; β-Glucosidase