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(The FASEB Journal. 2007;21:806.7)
© 2007 FASEB
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806.7

Dissecting the Activator Specificity of Rhodopseudomonas palustris ADP-Glucose Pyrophosphorylase

Baian Rabaia, Christine Nguyen, Diana Tran, Priscilla Antunez, Aaron Acero and Christopher R. Meyer

Chemistry and Biochemistry, California State University, Fullerton, 800 N. State College Blvd., Fullerton, CA, 92834

ABSTRACT

ADPGlucose pyrophosphorylases (ADPG PPases) catalyze a key step in glucan synthesis. The molecular basis for regulation of these enzymes is relatively unexplored. Engineering of the Rhodopseudomonas palustris (Rps.p.) ADPG PPase could increase capacity for carbon sequestration. The Rps.p. enzyme has been found to be activated by F6P and pyruvate and inhibited by FBP. The similar enzymes from E. coli and Rb. sphaeroides are activated by FBP and FBP, F6P, and pyruvate, respectively, while the enzyme from A. tumefaciens is activated by F6P and pyruvate but insensitive to FBP. Sequence alignments as well as the A. tumefaciens enzyme structure indicate that a region of the ß-helix C-terminal domain may be partly responsible for allosteric specificity. The A379R, E380G, K382V, and A385E proteins were successfully generated for characterization. Preliminary data showed that both K382V and A385E were still inhibited by FBP. E380G showed activation by FBP and F6P and A379R showed inhibition by FBP and insensitivity to F6P. The E380G enzyme also exhibited increased heat stability (+ 10°C) compared to wild type. The E380G enzyme has been purified and kinetic characterization is underway. The C-terminus of the Rps.p. enzyme clearly plays an important role in regulation as well as stability. Characterization of the A379R enzyme and the double mutant A379R, E380G is underway.

Supported in part by NSF Grant 0448676.





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