PubMed · 9434454
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
K Nakano. 1997. [Acarbose].. https://pubmed.ncbi.nlm.nih.gov/9434454/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
A proteinaceous inhibitor of alpha-amylase, Tendamistat, was evaluated as an immunogen to induce antibodies that mimic the enzyme activity and to investigate a new strategy to produce catalytic antibodies. Anti-Tendamistat polyclonal antibodies (pAbs) were shown to cross-react with acarbose, a strong carbohydrate inhibitor of alpha-amylases, and the alpha-amylase carbohydrate substrates, maltotetraose and maltoheptaose. Catalytic features of pAbs were characterized after denaturing natural serum alpha-amylase by treatment at pH 10 and in the presence of EDTA. A significant residual alpha-amylase activity was detected and associated with the IgG fraction, demonstrating that some antibodies behave as a functional mimic of natural amylase. Such antibodies, which behave as an "internal image" of the alpha-amylase, were used as immunogens to elicit anti-idiotype antibodies. It was demonstrated that the anti-idiotype antiserum contains a significant amount of antibodies that bind to porcine pancreatic amylase, which shows that they contain structural information from the original hapten, Tendamistat.
Explore the source record for details and available documents.
4-alpha-Glucanotransferase (GTase) is an essential enzyme in alpha-1,4-glucan metabolism in bacteria and plants. It catalyses the transfer of maltooligosaccharides from an 1,4-alpha-D-glucan molecule to the 4-hydroxyl group of an acceptor sugar molecule. The crystal structures of Thermotoga maritima GTase and its complex with the inhibitor acarbose have been determined at 2.6A and 2.5A resolution, respectively. The GTase structure consists of three domains, an N-terminal domain with the (beta/alpha)(8) barrel topology (domain A), a 65 residue domain, domain B, inserted between strand beta3 and helix alpha6 of the barrel, and a C-terminal domain, domain C, which forms an antiparallel beta-structure. Analysis of the complex of GTase with acarbose has revealed the locations of five sugar-binding subsites (-2 to +3) in the active-site cleft lying between domain B and the C-terminal end of the (beta/alpha)(8) barrel. The structure of GTase closely resembles the family 13 glycoside hydrolases and conservation of key catalytic residues previously identified for this family is consistent with a double-displacement catalytic mechanism for this enzyme. A distinguishing feature of GTase is a pair of tryptophan residues, W131 and W218, which, upon the carbohydrate inhibitor binding, form a remarkable aromatic "clamp" that captures the sugar rings at the acceptor-binding sites +1 and +2. Analysis of the structure of the complex shows that sugar residues occupying subsites from -2 to +2 engage in extensive interactions with the protein, whereas the +3 glucosyl residue makes relatively few contacts with the enzyme. Thus, the structure suggests that four subsites, from -2 to +2, play the dominant role in enzyme-substrate recognition, consistent with the observation that the smallest donor for T.maritima GTase is maltotetraose, the smallest chain transferred is a maltosyl unit and that the smallest residual fragment after transfer is maltose. A close similarity between the structures of GTase and oligo-1,6-glucosidase has allowed the structural features that determine differences in substrate specificity of these two enzymes to be analysed.