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B6db references: 199885156

type Journal Article
authors Takata, H.; Takaha, T.; Okada, S.; Takagi, M.; Imanaka, T.;
title Purification and characterization of alpha-glucan phosphorylase from Bacillus stearothermophilus
journal J. Ferment Bioeng
sel selected
ui 199885156
year (1998)
volume 85
pages 156-161
abstract α-Glucan phosphorylase (GP, EC catalyzes the reversible phosphorolysis of glucan and is considered to play a central role in the mobilization of carbohydrate reserves. The structural gene for GP has already been cloned and sequenced from Bacillus stearothermophilus TRBE14 [Takata et al., J. Bacteriol., 179, 46894698 1997; DDBJ/EMBL/GenBank accession No. D87026]. This enzyme was expressed in Escherichia coli and purified to homogeneity, and its enzymatic properties were analyzed. At pH 7, GP was stable up to 40C, and the optimum temperature for activity was 50C. The enzyme was stable in the pH range 6.5 to 11, and the optimum pH was 7. A test of substrate preference demonstrated that starch and glycogen were more reactive substrates than linear maltodextrin. The smallest acceptor for a synthetic reaction was maltotetraose (G4), and G4 was left as a final product after the phosphorolysis of a linear saccharide. ADP-glucose and UDP-glucose strongly inhibted this enzyme activity. Although the substrate specificity and type of inhibitors are similar to those of its counterpart from E. coli, B. stearothermophilus GP had about a 100-fold higher affinity, and much higher specific activity for glycogen than the E. coli enzyme. These results suggest that the rates of glycogen degradation in the two species may be different from each other.
last changed 2009/01/12 19:39

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