Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:2.3.3.1 (
citrate synthase
)
4,488
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The fluorescence polarization of 8-hydroxypyrene (1,3,6)trisulfonate (
HPT
) increases upon interaction with pig heart
citrate synthase
. Titration of
HPT
with increasing concentrations of
citrate synthase
exhibits a hyperbolic saturation behavior, from which the dissociation constant of the enzyme-
HPT
complex (3.64 +/- 0.3 microM) was determined. The enzyme-
HPT
interaction is competitively inhibited by oxaloacetate (but not affected by acetyl CoA) with a Ki of 4.3 +/- 1.8 microM. This value is similar to the dissociation constant (Kd = 4.5 +/- 1.6 microM) for the enzyme-oxalocetate complex (determined in the absence of any effector ligand), as well as to the Km for oxaloacetate (3.9 +/- 0.7 microM) in a steady-state
citrate synthase
catalyzed reaction at a saturating concentration of acetyl CoA. However, the dissociation constant for the
citrate synthase
-oxaloacetate complex determined by the urea denaturation method is at least 25-fold lower than those determined by the other methods. This suggests an effector role of urea in strengthening the enzyme-oxaloacetate interaction. At low nondenaturing concentrations, urea inhibits the
citrate synthase
catalyzed reaction in an uncompetitive manner with respect to oxaloacetate, i.e., the Km for oxaloacetate decreases with an increase in urea concentration. This further suggests that urea stabilizes the interaction between
citrate synthase
and oxaloacetate. The effect of urea is specific for the substrate oxaloacetate, and not for the substrate analogue,
HPT
, although both these ligands bind
citrate synthase
with equal affinities, and protect the enzyme against thermal denaturation with equal magnitudes. The results presented herein are discussed in the light of known conformational states of the enzyme.
...
PMID:Interaction of ligands with pig heart citrate synthase: conformational changes and catalysis. 165 9
