title: Inhibition of dextransucrase by Zn2+, Ni2+, Co2+, and Tris(hydroxymethyl)aminomethane (Tris).
abstract: Initial rate kinetics of polysaccharide formation indicate that Zn2+, Ni2+, and Co2+ inhibit dextransucrase [sucrose: 1,6-alpha-D-glucan 6-alpha-D-glucosyltransferase, EC 2.4.1.5] by binding to two types of metal ion sites. One type consists of a single site and has a low apparent affinity for Ca2+. At the remaining site(s), Ca2+ has a much higher apparent affinity than Zn2+, Ni2+, or Co2+, and prevents inhibition by these metal ions. These findings are consistent with a two-site model previously proposed from studies with Ca2+ and EDTA. Initial rate kinetics also show that Tris is competitive with sucrose, but that, unlike Zn2+, Tris does not bind with significant affinity to a second site. This argues that there is a site which is both the sucrose binding site and a general cation site.
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent; D003035:Cobalt / Q000494:pharmacology*; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors*; D007700:Kinetics; D008970:Molecular Weight; D009532:Nickel / Q000494:pharmacology*; D011489:Protein Denaturation / Q000187:drug effects; D014325:Tromethamine / Q000494:pharmacology*; D015032:Zinc / Q000494:pharmacology*
chemical_list: D002413:Cations, Divalent; D014325:Tromethamine; D003035:Cobalt; D009532:Nickel; D005964:Glucosyltransferases; C020025:dextransucrase; D015032:Zinc; D002118:Calcium