title: Amylomaltase of Pyrobaculum aerophilum IM2 produces thermoreversible starch gels.
abstract: Amylomaltases are 4-alpha-glucanotransferases (EC 2.4.1.25) of glycoside hydrolase family 77 that transfer alpha-1,4-linked glucans to another acceptor, which can be the 4-OH group of an alpha-1,4-linked glucan or glucose. The amylomaltase-encoding gene (PAE1209) from the hyperthermophilic archaeon Pyrobaculum aerophilum IM2 was cloned and expressed in Escherichia coli, and the gene product (PyAMase) was characterized. PyAMase displays optimal activity at pH 6.7 and 95 degrees C and is the most thermostable amylomaltase described to date. The thermostability of PyAMase was reduced in the presence of 2 mM dithiothreitol, which agreed with the identification of two possible cysteine disulfide bridges in a three-dimensional model of PyAMase. The kinetics for the disproportionation of malto-oligosaccharides, inhibition by acarbose, and binding mode of the substrates in the active site were determined. Acting on gelatinized food-grade potato starch, PyAMase produced a thermoreversible starch product with gelatin-like properties. This thermoreversible gel has potential applications in the food industry. This is the first report on an archaeal amylomaltase.
authors.affiliation: Centre for Carbohydrate Bioengineering TNO-University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands.
authors.forename: Thijs
authors.initials: T
authors.lastname: Kaper
authors.forename: Boguslawa
authors.initials: B
authors.lastname: Talik
authors.forename: Thijs J
authors.initials: TJ
authors.lastname: Ettema
authors.forename: Herman
authors.initials: H
authors.lastname: Bos
authors.forename: Marc J E C
authors.initials: MJ
authors.lastname: van der Maarel
authors.forename: Lubbert
authors.initials: L
authors.lastname: Dijkhuizen
mesh_terms: D001665:Binding Sites; D003001:Cloning, Molecular; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D019649:Food Industry / Q000379:methods; D005782:Gels / Q000378:metabolism; D006004:Glycogen Debranching Enzyme System / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D041543:Pyrobaculum / Q000201:enzymology* / Q000235:genetics; D013213:Starch / Q000378:metabolism
chemical_list: D005782:Gels; D006004:Glycogen Debranching Enzyme System; D013213:Starch; C020569:4 alpha-glucanotransferase