Allosteric regulation of the higher plant ADP-glucose pyrophosphorylase is a product of synergy between the two subunits.
The higher plant ADP-glucose pyrophosphorylase (AGPase) is a heterotetramer consisting of two regulatory large subunits (LSs) and two catalytic small subunits (SSs). To further characterize the roles of these subunits in determining enzyme function, different combinations of wildtype LS (LWT) and variant forms (LUpReg1, LM345) were co-expressed with wildtype SS (SWT) and variant forms (STG-15 and Sdevo330) and their enzyme properties compared to those measured for the heterotetrameric wildtype enzyme and SS homotetrameric enzymes. Analysis of the allosteric regulatory properties of the various enzymes indicates that although the LS is required for optimal activation by 3-phosphoglyceric acid and resistance to Pi, the overall allosteric regulatory and kinetic properties are specified by both subunits. Our results show that the regulatory and kinetic properties of AGPase are not simply due to the LS modulating the properties of the SS but, instead, are a product of synergistic interaction between the two subunits.
Hwang
Seon-Kap
SK
Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
Salamone
Peter R
PR
Okita
Thomas W
TW
D000494:Allosteric Regulation; D002384:Catalysis; D004789:Enzyme Activation; D015870:Gene Expression; D051599:Glucose-1-Phosphate Adenylyltransferase; D007700:Kinetics; D009154:Mutation / Q000235:genetics; D009713:Nucleotidyltransferases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010944:Plants / Q000145:classification / Q000201:enzymology*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
D010940:Plant Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase