title: Inhibition of inorganic pyrophosphatase of animal mitochondria by calcium.
abstract: Calcium ion is an uncompetitive inhibitor of the inorganic pyrophosphatases of bovine heart and rat liver mitochondria with respect to substrate MgPPi at pH 8.5 and a non-competitive inhibitor of the former enzyme at pH 7.2. The concentration of Ca2+ required to decrease the maximal velocities for both enzymes at pH 8.5, 0.4 mM Mg2+ was about 10 microM. The inhibition results from the binding of two Ca2+ ions to both free enzymes and their complexes with the substrate. The results suggest that Ca2+ regulates pyrophosphatase activity and hence PPi level in mammalian mitochondria.
authors.affiliation: A. N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, USSR.
authors.forename: A A
authors.initials: AA
authors.lastname: Baykov
authors.forename: S E
authors.initials: SE
authors.lastname: Volk
authors.forename: A
authors.initials: A
authors.lastname: Unguryte
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D008930:Mitochondria, Liver / Q000201:enzymology*; D011755:Pyrophosphatases / Q000037:antagonists & inhibitors*; D051381:Rats
chemical_list: D011755:Pyrophosphatases; D002118:Calcium