title: Interaction of divalent metal ions with Zn(2+)-glycerophosphocholine cholinephosphodiesterase from ox brain.
abstract: The effect of divalent metal ions on the activity of glycerophosphocholine cholinephosphodiesterse from ox brain was examined. Zn(2+)- and Co(2+)-glycerophosphocholine cholinephosphodiesterases were prepared from the exposure of apoenzyme to Zn2+ and Co2+, respectively, and the properties of two metallo-phosphodiesterases were compared to those of native phosphodiesterase. Although two metallo-enzymes were similar in expressing Km value, optimum pH or sensitivity to Cu2+, they differed in the susceptibility to the inhibition by thiocholine or tellurite; while Co(2+)-phosphodiesterase was more sensitive to tellurites, Zn(2+)-phosphodiesterase was more susceptible to inhibition by thiocholine. In addition, Zn(2+)-phosphodiesterase was more thermo-stable than Co2+ enzyme. Separately, when properties of native phosphodiesterase were compared to those of each metallo-phosphodiesterase, native phosphodiesterase was found to be quite similar to Zn(2+)-phosphodiesterase in many respects. Even in thermo-stability, native enzyme resembled Zn(2+)-phosphodiesterase rather than Co(2+)-enzyme. Consistent with this, the stability of native phosphodiesterase was maintained in the presence of Zn2+, but not Co2+, Mn2+ was also as effective as Zn2+ in the stabilization of the enzyme. Noteworthy, the native enzyme was found to be inhibited competitively by Cu2+ with a Ki value of 20 microM, and its inhibitory action was antagonized effectively by Zn2+ or Co2+. Also, choline, another competitive inhibitor of the enzyme, appeared to antagonize the inhibitory action of Cu2+. Taken together, it is suggested that there may be multiple binding sites for divalent metal ions in the molecule of glycerophosphocholine cholinephosphodiesterase.
authors.affiliation: College of Pharmacy, Department of Food and Nutrition, Chungnam National University, Taejeon, Korea.
authors.forename: K J
authors.initials: KJ
authors.lastname: Lee
authors.forename: M R
authors.initials: MR
authors.lastname: Kim
authors.forename: Y B
authors.initials: YB
authors.lastname: Kim
authors.forename: P K
authors.initials: PK
authors.lastname: Myung
authors.forename: D E
authors.initials: DE
authors.lastname: Sok
mesh_terms: D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology*; D001923:Brain Chemistry / Q000187:drug effects; D002413:Cations, Divalent; D002417:Cattle; D003035:Cobalt / Q000378:metabolism / Q000494:pharmacology; D003300:Copper / Q000378:metabolism / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D008566:Membranes / Q000187:drug effects / Q000201:enzymology; D019216:Metals, Heavy / Q000378:metabolism* / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000187:drug effects / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D019216:Metals, Heavy; D003035:Cobalt; D003300:Copper; D010727:Phosphoric Diester Hydrolases; C061931:glycerophosphocholine cholinephosphodiesterase; D015032:Zinc