Binding of [35S]lanthionine ketimine to bovine brain membranes.

Lanthionine ketimine (LK), cystathionine ketimine (CK) and thialisine ketimine (AECK) represent a new class of cyclic sulfur-containing iminoacids recently identified in the CNS and humane urine. These natural compounds have been synthesized and chemically characterized in our laboratories. In order to define the role of these iminoacids as putative neuromodulators we made ready the synthesis and the purification of [35S]LK. Binding experiments performed on bovine cerebral membranes indicate the presence of a ligand site for LK, exhibiting the basic criteria of saturability and reversibility typical of a receptor-ligand system. Scatchard analysis indicates the presence of a single population of sites with an affinity constant of about 30 nM; binding is maximal between pH 7-7.5 and it is scarcely affected by ionic strength and ionic composition. Funher studies are in progress to characterize the specificity of binding by displacement experiments in the precence of known neuroactive agonists or antagonists.