title: Modulation of cyclizing activity and thermostability of cyclodextrin glucanotransferase and its application as an antistaling enzyme.
abstract: Cyclodextrin glucanotransferase from Bacillus stearothermophilus ET1 (CGTase ET1) is a potential antistaling enzyme with cyclodextrin (CD)-forming activity. To reduce cyclization activity of CGTase ET1, phenylalanine residues at 191 and 255 were replaced with a glycine (F191G-CGTase ET1) and an isoleucine (F255I-CGTase ET1), respectively. Temperature optima of both mutant enzymes were lower than that of the wild-type. Cyclization activities of both mutants decreased dramatically, but F255I-CGTase ET1 showed a 2-fold higher hydrolytic activity than the wild-type enzyme. CD content of bread loaf treated with F191G-CGTase ET1 was 28.6% of that treated with wild-type, whereas no CD was detected in the loaf treated with F255I-CGTase ET1. Loaves treated with CGTase ET1 or either of the two mutants contained more of the larger maltooligosaccharides such as maltopentaose and maltohexaose than the control and the commercial antistaling enzyme-treated loaves. Retrogradation rates decreased significantly in the loaves treated with either mutant, which indicates the applicability of CGTase ET1 in the bread industry by modulating the cyclizing and hydrolyzing activities of the enzyme.
authors.affiliation: Research Center for New Bio-Materials in Agriculture and Department of Food Science and Technology, School of Agricultural Biotechnology, Seoul National University, Suwon 441-744, Korea.
authors.forename: Sung-Ho
authors.initials: SH
authors.lastname: Lee
authors.forename: Young-Wan
authors.initials: YW
authors.lastname: Kim
authors.forename: Suyong
authors.initials: S
authors.lastname: Lee
authors.forename: Joong-Hyuck
authors.initials: JH
authors.lastname: Auh
authors.forename: Sung-Suk
authors.initials: SS
authors.lastname: Yoo
authors.forename: Tae-Jip
authors.initials: TJ
authors.lastname: Kim
authors.forename: Jung-Wan
authors.initials: JW
authors.lastname: Kim
authors.forename: Sun-Tae
authors.initials: ST
authors.lastname: Kim
authors.forename: Hoe-Jin
authors.initials: HJ
authors.lastname: Rho
authors.forename: Jin-Hwan
authors.initials: JH
authors.lastname: Choi
authors.forename: Young-Bae
authors.initials: YB
authors.lastname: Kim
authors.forename: Kwan-Hwa
authors.initials: KH
authors.lastname: Park
mesh_terms: D001939:Bread; D003500:Cyclization; D003505:Cyclodextrins / Q000378:metabolism; D004795:Enzyme Stability; D005519:Food Preservation; D001411:Geobacillus stearothermophilus / Q000201:enzymology; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D003505:Cyclodextrins; D011994:Recombinant Proteins; D005964:Glucosyltransferases; C019963:cyclomaltodextrin glucanotransferase