Monovalent Cations and Striatal Tyrosine Hydroxylase

Abstract

The kinetic properties of soluble tyrosine hydroxylase [EC 1.14.16.2] from rat striatum and the activation of the enzyme by the polyanion heparin were assessed as a function of the monovalent cations K+, Na+, tetramethylammonium (TMA+) and Tris. Substitution of K+ or Na+ for TMA+ or Tris can alter the kinetic properties of tyrosine hydroxylase in the absence of heparin, the nature of the interaction of the enzyme with heparin, and also the kinetic properties of the heparin-activated enzyme. Monovalent cations can probably support unique conformational states of the enzyme.