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 α-1,4-linked glucans or malto-oligosaccharides to other α-1,4-linked glucans, maltooligosaccharides 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-α-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.
|Number of pages||8|
|Journal||Biologia. Section: Cellular and Molecular Biology|
|Issue number||SUPPL. 11|
|Publication status||Published - 2002|
- Crystal structure
- Thermotoga maritima
- Transfer specificity