title: Comparative analyses of two thermophilic enzymes exhibiting both beta-1,4 mannosidic and beta-1,4 glucosidic cleavage activities from Caldanaerobius polysaccharolyticus.
abstract: The hydrolysis of polysaccharides containing mannan requires endo-1,4-beta-mannanase and 1,4-beta-mannosidase activities. In the current report, the biochemical properties of two endo-beta-1,4-mannanases (Man5A and Man5B) from Caldanaerobius polysaccharolyticus were studied. Man5A is composed of an N-terminal signal peptide (SP), a catalytic domain, two carbohydrate-binding modules (CBMs), and three surface layer homology (SLH) repeats, whereas Man5B lacks the SP, CBMs, and SLH repeats. To gain insights into how the two glycoside hydrolase family 5 (GH5) enzymes may aid the bacterium in energy acquisition and also the potential application of the two enzymes in the biofuel industry, two derivatives of Man5A (Man5A-TM1 [TM1 stands for truncational mutant 1], which lacks the SP and SLH repeats, and Man5A-TM2, which lacks the SP, CBMs, and SLH repeats) and the wild-type Man5B were biochemically analyzed. The Man5A derivatives displayed endo-1,4-beta-mannanase and endo-1,4-beta-glucanase activities and hydrolyzed oligosaccharides with a degree of polymerization (DP) of 4 or higher. Man5B exhibited endo-1,4-beta-mannanase activity and little endo-1,4-beta-glucanase activity; however, this enzyme also exhibited 1,4-beta-mannosidase and cellodextrinase activities. Man5A-TM1, compared to either Man5A-TM2 or Man5B, had higher catalytic activity with soluble and insoluble polysaccharides, indicating that the CBMs enhance catalysis of Man5A. Furthermore, Man5A-TM1 acted synergistically with Man5B in the hydrolysis of beta-mannan and carboxymethyl cellulose. The versatility of the two enzymes, therefore, makes them a resource for depolymerization of mannan-containing polysaccharides in the biofuel industry. Furthermore, on the basis of the biochemical and genomic data, a molecular mechanism for utilization of mannan-containing nutrients by C. polysaccharolyticus is proposed.
authors.affiliation: Energy Biosciences Institute, University of Illinois, Urbana, IL 61801, USA.
authors.forename: Yejun
authors.initials: Y
authors.lastname: Han
authors.forename: Dylan
authors.initials: D
authors.lastname: Dodd
authors.forename: Charles W
authors.initials: CW
authors.lastname: Hespen
authors.forename: Samuel
authors.initials: S
authors.lastname: Ohene-Adjei
authors.forename: Charles M
authors.initials: CM
authors.lastname: Schroeder
authors.forename: Roderick I
authors.initials: RI
authors.lastname: Mackie
authors.forename: Isaac K O
authors.initials: IK
authors.lastname: Cann
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D020134:Catalytic Domain; D002480:Cellulase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004795:Enzyme Stability; D005936:Glucans / Q000378:metabolism*; D006094:Gram-Positive Bacteria / Q000201:enzymology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008361:Mannosidases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000378:metabolism*; D021382:Protein Sorting Signals; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005936:Glucans; D011134:Polysaccharides; D021382:Protein Sorting Signals; C040088:1,4-glucan; D008361:Mannosidases; D002480:Cellulase; C041867:endo-1,4-beta-D-mannanase