title: A laminaribiose-hydrolyzing enzyme, AkLab, from the common sea hare Aplysia kurodai and its transglycosylation activity.
abstract: Endo-β-1,3-glucanases (laminarinase, EC 3.2.1.6) from marine molluscs specifically degrades laminarin from brown algae producing laminaribiose and glucose, but hardly degrades laminaribiose. For the complete depolymerization of laminarin, other enzymes that can hydrolyze laminaribiose appear to be necessary. In the present study, we successfully isolated a laminaribiose-hydrolyzing enzyme from the digestive fluid of a marine gastropod Aplysia kurodai by ammonium sulfate fractionation followed by conventional column chromatographies. This enzyme, AkLab, named after the scientific name of this animal and substrate specificity toward laminaribiose, shows an approximate molecular mass of 110kDa on SDS-PAGE, and optimum pH and temperature at around pH5.5 and 50°C, respectively. AkLab rapidly hydrolyzes laminaribiose and p-nitrophenyl-β-D-glucoside, and slowly cellobiose, gentiobiose and lactose, but not sucrose and maltose. AkLab shows high transglycosylation activity and can produce a series of laminarioligosaccharides larger than laminaritetraose from laminaribiose (a donor substrate) and laminaritriose (an acceptor substrate). This enzyme is suggested to be a member of glycosyl hydrolase family 1 by the analysis of partial amino-acid sequences.
authors.affiliation: Laboratory of Marine Biotechnology and Microbiology, Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho 3-1-1, Hakodate 041-8611, Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Kumagai
authors.forename: Takuya
authors.initials: T
authors.lastname: Satoh
authors.forename: Akira
authors.initials: A
authors.lastname: Inoue
authors.forename: Takao
authors.initials: T
authors.lastname: Ojima
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia / Q000201:enzymology*; D004187:Disaccharides / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000378:metabolism*; D006031:Glycosylation; D006868:Hydrolysis; D008969:Molecular Sequence Data; D013379:Substrate Specificity
chemical_list: D004187:Disaccharides; C014637:laminaribiose; D006026:Glycoside Hydrolases
keywords: Aplysia; Gastropod; Laminaribiose; Sea hare; β-Glucosidase