Purification and Characterization of α-Glucan Phosphorylase from Bacillus stearothermophilus

概要

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α-Glucan phosphorylase(GP, EC 2.4.1.1)catalyzes the reversible phosphorolysis of glucan and is considered to phs a central role in the mobilization of carbohydrate reseryes. The structural gene for GP has already been cloned and sequenced from Bacillus stearothermophilus TRBE14 [Takata et al. , J. Bacteriol. , 179, 4689-4698, 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 tip tt 40℃, and the optimum temperature for activity was 50℃. 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 glyeogen 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 saccbride. ADP-glucose and UDP-glucose strongly inhibited this enzyme activity. Although the substrate specificity and type of inhibitors are similar to those of its counterprt 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.
社団法人日本生物工学会の論文
1998-02-25