title: Purification and characterization of cellulase from North Pacific krill (Euphausia pacifica). Analysis of cleavage specificity of the enzyme.
abstract: Krill are filter feeders that consume algae, plankton and detritus, indicating that krill possess an adequate cellulose digesting system. However, less is known about the enzymatic properties of crustacean cellulases compared to termite cellulases. In the present study, 48 kDa-cellulase was highly purified from krill (Euphausia pacifica) in an effort to determine the cleavage specificity of the enzyme. The most notable characteristic of the enzyme was its high activity against both lichenan and carboxymethyl cellulose. The enzyme hydrolyzed internal β-1,4 glycosidic bonds within lichenan as well as carboxymethyl cellulose to release oligosaccharides and glucose. The effects of pH and temperature on the activity and stability of both enzyme activities were almost identical. Cello-oligosaccharides with a degree of polymerization of 4-6 were hydrolyzed by the enzyme, and the same endo-products, cellotriose, cellobiose and glucose, were produced from these oligosaccharides. Neither cellotriose nor cellobiose was hydrolyzed by the enzyme. The enzyme digested filter paper and sea lettuce to produce cellobiose, cellotriose and glucose as major products. Although amino acid sequence homology of the enzyme with termite cellulases and the presence of oligosaccharides in the enzyme suggested that the enzyme is produced by krill itself, further analysis is necessary.
authors.affiliation: Department of Biological Science and Technology, The University of Tokushima Graduate School, 2-1 Minamijosanjima, Tokushima 770-8506, Japan. tsuji@bio.tokushima-u.ac.jp
authors.forename: Akihiko
authors.initials: A
authors.lastname: Tsuji
authors.forename: Shiori
authors.initials: S
authors.lastname: Sato
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kondo
authors.forename: Keiko
authors.initials: K
authors.lastname: Tominaga
authors.forename: Keizo
authors.initials: K
authors.lastname: Yuasa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002266:Carboxymethylcellulose Sodium / Q000378:metabolism; D002480:Cellulase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D033201:Euphausiacea / Q000201:enzymology* / Q000382:microbiology; D005374:Filtration; D005936:Glucans / Q000378:metabolism; D007422:Intestines / Q000201:enzymology / Q000382:microbiology; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000378:metabolism; D010209:Paper; D012624:Seaweed / Q000378:metabolism; D017421:Sequence Analysis; D013379:Substrate Specificity; D013559:Symbiosis
chemical_list: D005936:Glucans; D009844:Oligosaccharides; D002480:Cellulase; D002266:Carboxymethylcellulose Sodium; C015968:lichenin