[Interaction of terbium ions with inorganic pyrophosphatase from bakers' yeast: characterization of the binding sites].
Terbium ions bind with a 2:1 stoichiometry per subunit to inorganic pyrophosphatase from bakers' yeast (EC 3.6.1.1) as measured by an increase of terbium fluorescence. The Tb3+ inhibition of the Mg2+ activated pyrophosphate hydrolysis is caused by a competitive binding at the substrate site of the active centre. The second Mg2+ binding site--the so-called "stabilization site"--is discussed as an additional binding site for Tb3+. Thereby, Tb3+ causes also a stabilization of the enzyme against heat denaturation. The dissociation constants of the terbium-pyrophosphatase interaction are in the micromolar range.
D001665:Binding Sites; D001667:Binding, Competitive; D006358:Hot Temperature; D008274:Magnesium / Q000378:metabolism; D011755:Pyrophosphatases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013725:Terbium / Q000378:metabolism* / Q000494:pharmacology
D013725:Terbium; D011755:Pyrophosphatases; D008274:Magnesium
Wechselwirkung von Tb3+ mit anorganischer Pyrophosphatase aus Bäckerhefe: Charakterisierung der Bindungsorte.