期刊
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
卷 537, 期 2, 页码 210-216出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.abb.2013.07.019
关键词
ADP-glucose pyrophosphorylase; Phosphate inhibition; Mechanism; Allosteric regulation
资金
- National Science Foundation [IBM 0444031, IOS 0815104]
- USDA Competitive Grants Program [2006-35100-17220, 2008-35318-18649]
- National Institute of Food and Agriculture [2010-04228]
- U.S. Department of Energy [DE-FG02-12ER20216]
ADP-glucose pyrophosphorylase (AGPase) is highly regulated by allosteric effectors acting both positively and negatively. Enzymes from various sources differ, however, in the mechanism of allosteric regulation. Here, we determined how the effector, inorganic phosphate (Pi), functions in the presence and absence of saturating amounts of the activator, 3-phosphoglyceric acid (3-PGA). This regulation was examined in the maize endosperm enzyme, the oxidized and reduced forms of the potato tuber enzyme as well as a small subunit chimeric AGPase (MP), which contains both maize endosperm and potato tuber sequences paired with a wild-type maize large subunit. These data, combined with our previous kinetic studies of these enzymes led to a model of Pi inhibition for the various enzymes. The Pi inhibition data suggest that while the maize enzyme contains a single effector site that binds both 3-PGA and Pi, the other enzymes exhibit more complex behavior and most likely have at least two separate interacting binding sites for Pi. The possible physiological implications of the differences in Pi inhibition distinguishing the maize endosperm and potato tuber AGPases are discussed. (C) 2013 Elsevier Inc. All rights reserved.
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