Biologia, Bratislava, 57/Suppl. 11: 101-108, 2002.
ISSN 0006-3088 (Biologia).
Biochemical properties and structural features of the thermostable maltodextrin transglycosidases from Thermotoga maritima.
Carsten Raasch1, Anna Roujeinikova2, Harald Meissner1, David W. Rice2 & Wolfgang Liebl1*
1 Institute of Microbiology and Genetics, Georg-August-University, Grisebachstr. 8, D-37077 Goettingen, Germany; tel.: ++ 49 551 393795, fax: ++ 49 551 394897, e-mail: email@example.com
2 Krebs Institute for Biomolecular Research, The University of Sheffield, England
Received: October 4, 2001 / Accepted: March 4, 2002
Maltosyltransferase (MTase) is an extremely thermostable enzyme which, based on its primary structure, is classified into glycoside hydrolase family 13. The enzyme is a non-hydrolytic transglycosidase (maltodextrin glycosyltransferase, MGTase) which catalyses the transfer of maltosyl units from a-1,4-linked glucans or malto-oligosaccharides to other a-1,4-linked glucans, malto-oligosaccharides or glucose. MTase represents the first exo-MGTase known. To date, the only organism known to produce a starch-converting enzyme with this unique reaction chemistry is the hyperthermophilic bacterium Thermotoga maritima, a strictly anaerobic heterotroph with a maximum growth temperature of 90 °C. In addition to MTase, T. maritima possesses a second MGTase, 4-a-glucanotransferase (GTase), also a member of the glycoside hydrolase family 13. In contrast to MTase, GTase displays a broad transfer specificity. Recently, crystals of recombinant MTase and GTase have been obtained by the hanging-drop vapor-diffusion method, and the crystal structures of MTase and its complex with maltose have been determined at 2.4 and 2.1 Å resolution, respectively. In this communication, the enzymatic characteristics of MTase and GTase are reviewed, and structural features, possibly of importance for the unique transfer specificity and thermostability of MTase, are discussed.
Key words: Thermotoga maritima, transglycosidase, maltosyltransferase, 4-a-glucanotransferase, amylase, crystal structure, transfer specificity.