Amylomaltase of Pyrobaculum aerophilum IM2 produces thermoreversible starch gels.
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.
Kaper
Thijs
T
Centre for Carbohydrate Bioengineering TNO-University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands.
Talik
Boguslawa
B
Ettema
Thijs J
TJ
Bos
Herman
H
van der Maarel
Marc J E C
MJ
Dijkhuizen
Lubbert
L
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
D005782:Gels; D006004:Glycogen Debranching Enzyme System; D013213:Starch; C020569:4 alpha-glucanotransferase