Amino acids with maltose

The simplest modification is to place a destabilizing amino acid at the N-terminal end according to the N-end rule (Varshavsky, 1992). This can be done by expressing the protein as a fusion protein, e.g. with maltose binding protein behind a cleavage site specific for a rare-cutting protease, such as factor Xq. In this case the N-terminal amino acid can be any amino acid except proline. 

As a variant of the studies discussed above, Lecroisey et al.1] undertook an NMR study of the 11 amino acid C3 epitope from poliovirus VP1 following its insertion at eight different sites into maltose-binding protein (MBP) (mass 41 kDa). The insertion of this epitope at the various sites did not cause significant structural changes to the protein so as to affect its ability to function normally and bind maltose. From H NMR studies of these mutants, it was found that the epitope had significant conformational flexibility and that the mobility was maintained regardless of where it was placed into the protein.71 Consistent with this mobility, the epitope adopted no ordered conformation in any of the mutants. 

Chromatographic batch reactors are employed to prepare instable reagents on the laboratory scale (Coca et al., 1993) and for the production of fine chemicals. These applications include the racemic resolution of amino acid esters (Kalbe et al., 1989), acid-catalyzed sucrose inversion (Lauer, 1980), production of dextran (Zafar and Barker, 1988) and saccharification of starch to maltose (Sarmidi and Barker, 1993a). Sardin et al. (1993) employed batch chromatographic reactors for different esterification reactions such as the esterification of acetic acid with ethanol and the transesterification of methylacetate. Falk and Seidel-Morgenstern (2002) have investigated the hydrolysis of methyl formate. 

A rather widespread family of proteins, found in the periplasmic space of gramnegative bacteria, complexes certain small molecules and allows them to be transported through the cell wall or activate chemotaxis. Each of these functions involves a consecutive interaction with specific membrane proteins. The molecules transported are amino acids, sulfate, mono- and oligosaccchrides. In this way ABP complexes L-arabinose (K 0.98 x 10 M), and MBP (maltodextrin-binding protein) complexes maltose (ATj 35 x 10 M) and maltodextrins. It is in this series that are found the strongest possible bonds between sugars and proteins. The dissociation rate ( i 1.5 s ) is indicative of the upper limit of the ionic transport rate. Hydrogen bonds... 

Fig. 3. Substrate binding site on Taka-amylase A deduced from electron density difference maps with the enzyme-maltose complex and model building. The seven saccharide binding sites are numbered. Presumed catalytic amino acids Asp-206 and Asp-297 surround the sessile glycoside bond. Glu-230 is considered as a possible catalytic amino acid as well because of its proximity to the reaction center. Adapted from Matsuura et al. (262) with permission from J. Biochem (Tokyo).

Goodwin J.C. (1983) Isolation of 3-0- -i>gluco- and 3-O-p-D-galacto pyranosyloxy-2-furyl methyl ketones from nonenzymic browing of maltose and lactose with secondary amino acids. Carbohydrate Res. 115, 281-7. 

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