The action mode of Thermus aquaticus YT-1 4-α-glucanotransferase and its chimeric enzymes introduced with starch-binding domain on amylose and amylopectin

• Published in: Carbohydrate polymers Vol. 67; no. 2; pp. 164 - 173
• Main Authors: Park, Jin-Hee, Kim, Hyun-Jung, Kim, Yung-Hee, Cha, Hyunju, Kim, Young-Wan, Kim, Tae-Jip, Kim, Yong-Ro, Park, Kwan-Hwa
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-01-2007; Elsevier Science
• Subjects: 4-α-glucanotransferase; Amylopectin; Amylose; Bacillus stearothermophilus; Biological and medical sciences; Biotechnology; Cyclo-amylose; Fundamental and applied biological sciences. Psychology; Starch-binding domain (SBD); Thermus aquaticus; Thermus aquaticus YT-1; Amylose; Thermus aquaticus YT-1; Amylopectin; Cyclo-amylose; 4-α-glucanotransferase; Starch-binding domain (SBD); 4-α-Glucanotransferase; Thermus aquaticus; Enzyme; Transferases; Glycosyltransferases; Bacteria; Hexosyltransferases
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2006.05.018

A thermostable 4-α-glucanotransferase (TAαGT) gene isolated from
Thermus aquaticus YT-1 had an open reading frame of 1503 nucleotides, which encoded 500 amino acid residues for a 57,969 dalton protein. The maximum activity of the TAαGT was observed at pH 7.5 and 70
°C. The enzyme catalyzed intermolecular transglycosylation of maltooligosaccharides (disproportionation) to produce linear α-1,4-glucans of various sizes. The starch-binding domains (SBD) of
Bacillus stearothermophilus ET1 CGTase (E and DE) were introduced into the C-terminus of TAαGT to enhance the starch utilizing activity. The chimeric enzymes, TAαGT-E and TAαGT-DE, showed no difference in temperature optimum, transglycosylation activity, and amylolytic degradation pattern compared to TAαGT wild-type. However, TAαGT-DE exhibited the highest molar specific activity toward amylose. TAαGT-DE modified amylopectin molecules by its disproportionating activities to produce modified amylopectin clusters (
M
w 10
5–10
6). Also, it demonstrated the ability to produce cyclo-amyloses with DP of 19 through 35 from amylose molecules.