Purification and characterization of a family 5 endoglucanase from a moderately thermophilic strain of Bacillus licheniformis.
Strains of thermophilic bacilli were screened for cellulolytic activity by gel diffusion assay on selective medium at 55 degrees C. Strain B-41361, identified as a strain of Bacillus licheniformis, displayed activity against carboxymethylcellulose. Zymogram analysis demonstrated several catalytically active polypeptides with the most prominent species having a mass of 37 kDa. The enzyme was purified 60-fold with a 17% yield and specific activity of 183 U/mg. The amino terminal sequence was homologous to members of glycoside hydrolase family 5. Optimal temperature was 65 degrees C (measured over 30 min), but the enzyme was most stable at 60 degrees C, retaining greater than 90% activity after one hour. The enzyme had a broad pH range, with maximal activity at pH 6.0, 75% maximal activity at pH 4.5, and 40% at pH 10. The enzyme hydrolyzed p-nitrophenylcellobioside, barley beta-glucan, and lichenan, but no activity was detected against avicel or acid-swollen cellulose.
Bischoff
Kenneth M
KM
U.S. Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, 1815 N. University St., Peoria, IL 61604, USA. bischoffk@ncaur.usda.gov
Rooney
Alejandro P
AP
Li
Xin-Liang
XL
Liu
Siqing
S
Hughes
Stephen R
SR
D001407:Bacillus / Q000201:enzymology*; D002480:Cellulase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D004795:Enzyme Stability; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D013379:Substrate Specificity
D002480:Cellulase; C019826:carboxymethylcellulase