Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of phosphate on the inhibition by 4-chloro-7-nitrobenzofurazan of the ATPase activity of the proton-translocating ATP synthase in heart submitochondrial particles was investigated. Binding of phosphate protected strongly against the inhibition. A dissociation constant of 0.2 mM was determined for the enzyme X Pi complex and shown to be independent of pH in the range 7.0-8.0. The protective effect of phosphate was mimicked by arsenate but not by sulphate or malonate. Similar results were obtained for the enzyme from Paracoccus denitrificans. 2,4-Dinitrophenol enhanced phosphate binding to the mitochondrial enzyme since the protective effect of phosphate was increased. The data are compatible with protection arising from binding of phosphate to a catalytic site.
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PMID:Characterisation of phosphate binding to mitochondrial and bacterial membrane-bound ATP synthase by studies of inhibition with 4-chloro-7-nitrobenzofurazan. 286 72

The activity and stability of carbamoyl-phosphate synthetase (EC 6.3.4.16) may involve hydrophobic and ionic bonds within the enzyme. The 1-anilino-8-naphthalene sulfonate (ANS) equilibrium binding method with hydrophobic and ionic sites in enzymes, therefore, seemed suitable for the study of the acetylglutamate activation and ATP binding of the enzyme. The enzyme had a high affinity for the dye but low fluorescent yields. The enzyme had 32-88 ANS binding sites, depending on combination with ATP and acetylglutamate, and individual affinity constants for each combination. Despite the large number of binding sites, the acetylglutamate and ATP concentrations for half-maximal fluorescent change (10-40 microM) corresponded to the high-affinity bound ATP (ATPB) and acetylglutamate Kd values. In kinetic studies, ANS competed with ATP or acetylglutamate. The extrapolated ANS Ki values for ATP or acetylglutamate were both 35 microM. This value agreed with the ANS Kd value of the enzyme X ATP conformation, indicating that this was the conformation competed for by ANS. Since ANS did not influence the HCO3-dependent ATPase, ANS was concluded to compete with the ATPB binding conformation and transitional changes. This study suggests that part of the activator role of acetylglutamate may be to change the tertiary structure of the enzyme to induce hydrophobic sites which are accessible to ANS and possibly at the ATPB site.
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PMID:Fluorescent probe study with 1-anilino-8-naphthalene sulfonate on acetylglutamate activation, ATP binding and conformational changes of the rat liver carbamoyl-phosphate synthetase. 687 Dec 32