Fluoride is a strong and specific inhibitor of (asymmetrical) Ap4A hydrolases

Abstract

Fluoride acts as a noncompetitive, strong inhibitor of (asymmetrical) Ap₄A hydrolases (EC 3.6.1.17). The K _i values estimated for the enzymes isolated from seeds of some higher plants (yellow lupin, sunflower and marrow) are in the range of 2–3 μM and I ₅₀ for the hydrolase from a mammalian tissue (beef liver) is 20 μM. The anion, up to 25 mM, does not affect the following other enzymes which are able to degrade the bis(5'-nucleosidyl)-oligophosphates: Escherichia coli (symmetrical) Ap₄A hydrolase (EC 3.6.1.41), yeast Ap₄A phosphorylase (EC 2.7.7.53), yellow lupin Ap₃A hydrolase (EC 3.6.1.29) and phosphodiesterase (EC 3.1.4.1). None of halogenic anions but fluoride affects the activity of (asymmetrical) Ap₄A hydrolases. Usefulness of the fluoride effect for the in vivo studies on the Ap₄A metabolism is shortly discussed.