title: Substrate binding properties of potato tuber ADP-glucose pyrophosphorylase as determined by isothermal titration calorimetry.
abstract: Substrate binding properties of the large (LS) and small (SS) subunits of potato tuber ADP-glucose pyrophosphorylase were investigated by using isothermal titration calorimetry. Our results clearly show that the wild type heterotetramer (S(WT)L(WT)) possesses two distinct types of ATP binding sites, whereas the homotetrameric LS and SS variant forms only exhibited properties of one of the two binding sites. The wild type enzyme also exhibited significantly increased affinity to this substrate compared to the homotetrameric enzyme forms. No stable binding was evident for the second substrate, glucose-1-phosphate, in the presence or absence of ATPγS suggesting that interaction of glucose-1-phosphate is dependent on hydrolysis of ATP and supports the Theorell-Chance bi bi reaction mechanism.
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA.
authors.forename: Bilal
authors.initials: B
authors.lastname: Cakir
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA.
authors.forename: Aytug
authors.initials: A
authors.lastname: Tuncel
authors.affiliation: School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA.
authors.forename: Abigail R
authors.initials: AR
authors.lastname: Green
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA.
authors.forename: Kaan
authors.initials: K
authors.lastname: Koper
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA.
authors.forename: Seon-Kap
authors.initials: SK
authors.lastname: Hwang
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA. Electronic address: okita@wsu.edu.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Okita
authors.affiliation: School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA. Electronic address: chkang@wsu.edu.
authors.forename: ChulHee
authors.initials: C
authors.lastname: Kang
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D015153:Blotting, Western; D002151:Calorimetry / Q000379:methods*; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000737:chemistry / Q000378:metabolism*; D005958:Glucosephosphates / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D035281:Plant Tubers / Q000201:enzymology*; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011198:Solanum tuberosum / Q000201:enzymology*; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: D005958:Glucosephosphates; D010940:Plant Proteins; D021122:Protein Subunits; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; C031590:glucose-1-phosphate; D051599:Glucose-1-Phosphate Adenylyltransferase
keywords: ADP-glucose pyrophosphorylase; Heterotetramer; Homotetramer; Isothermal titration calorimetry; Starch synthesis; Substrate binding properties