Structure and function of glucose dehydrogenase from Escherichia coli
University of Southampton, 1998
Online
Hochschulschrift
Zugriff:
Glucose dehydrogenase (GDH) is a membrane bound PQQ- containing quinoprotein which catalyses the oxidation of D-glucose to gluconolactone. In E. coli under growth conditions used so far, the enzyme is produced as the apo-form in the absence of added PQQ. This is due to the lack of PQQ production. The apo-enzyme can be reconstituted to the active holo-form by addition of PQQ and a divalent cation. Other PQQ-containing dehydrogenases include those that oxidase alcohol and methanol. Methanol dehydrogenase (MDH) of Methylobacterium extorquens is a soluble quinoprotein, whose X-ray structure (at 1.94Å) has recently been published. It has an α₂β₂ tetrameric structure; the α-subunit which contains the active site is a super-barrel having an 8-fold radial symmetry stabilised by a novel tryptophan-docking motif. The PQQ is held in place in the active site by a coplanar tryptophan and by a novel disulphide ring structure. Three types of alcohol dehydrogenase (ADH) have been identified. Sequence homology indicated that part of GDH and ADH may have equivalent super-barrel structures to MDH. In this work the sequences of the relevant parts of a type III ADH from Acetobacter aceti and GDH from E. coli were modelled onto the X-ray structure of MDH from Methylobacterium extorquens. Also the sequence of a proposed type I ADH from Azoarcus sp. BH72 was modelled onto the MDH structure. This work supported the suggestion that the enzymes have a similar structure, because many of the structural features found in MDH were conserved in the model ADH and GDH structures. Enzyme characterisation of the wild-type and mutant enzymes was carried out. This included substrate specificity, inhibitor studies and factors effecting reconstitution of the apo-enzyme. Sequence comparisons indicated that the membrane bound GDH was comprised of a membrane anchor and a periplasmic super-barrel domain similar in structure to the α-subunit of MDH.
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Structure and function of glucose dehydrogenase from Escherichia coli
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Autor/in / Beteiligte Person: | Cozier, Gyles Eldred |
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Veröffentlichung: | University of Southampton, 1998 |
Medientyp: | Hochschulschrift |
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