title: Kinetics of inactivation of green crab (Scylla Serrata) alkaline phosphatase during removal of zinc ions by ethylenediaminetetraacetic acid disodium.
abstract: Green crab (Scylla Serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme, the each active site in which contains a tight cluster of two zinc ions and one magnesium ion. The kinetic theory of the substrate reaction during irreversible inhibition of enzyme activity previously described by Tsou has been applied to a study on the kinetics of the course of inactivation of the enzyme by ethylenediaminetetraacetic acid disodium (EDTA). The kinetics of the substrate reaction with different concentrations of the substrate p-nitrophenyl phosphate (PNPP) and inactivator EDTA suggested a complexing mechanism for inactivation by, and substrate competition with, EDTA at the active site. The inactivation kinetics are single phasic, showing the initial formation of an enzyme-EDTA complex is a relatively rapid reaction, followed a slow inactivation step that probably involves a conformational change of the enzyme. Zinc ions are finally removed from the enzyme. The presence of metal ions apparently stabilizes an active-site conformation required for enzyme activity.
authors.affiliation: Department of Biology, Xiamen University, People's Republic of China.
authors.forename: Q X
authors.initials: QX
authors.lastname: Chen
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: H R
authors.initials: HR
authors.lastname: Wang
authors.forename: H M
authors.initials: HM
authors.lastname: Zhou
mesh_terms: D000469:Alkaline Phosphatase / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D003386:Brachyura / Q000201:enzymology*; D004492:Edetic Acid / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation; D007700:Kinetics; D011487:Protein Conformation; D013379:Substrate Specificity; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: D004492:Edetic Acid; D000469:Alkaline Phosphatase; D015032:Zinc