Modulation of cyclizing activity and thermostability of cyclodextrin glucanotransferase and its application as an antistaling enzyme.
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.
Lee
Sung-Ho
SH
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.
Kim
Young-Wan
YW
Lee
Suyong
S
Auh
Joong-Hyuck
JH
Yoo
Sung-Suk
SS
Kim
Tae-Jip
TJ
Kim
Jung-Wan
JW
Kim
Sun-Tae
ST
Rho
Hoe-Jin
HJ
Choi
Jin-Hwan
JH
Kim
Young-Bae
YB
Park
Kwan-Hwa
KH
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
D003505:Cyclodextrins; D011994:Recombinant Proteins; D005964:Glucosyltransferases; C019963:cyclomaltodextrin glucanotransferase