The formation of inositol phosphate derivatives by isolated membranes from Acer pseudoplatanus is stimulated by guanine nucleotides

AbstractMembranes isolated from Acer pseudoplatanus cell suspension cultures that were prelabelled with [3H]inositol are able to release different water-soluble phosphoinositol derivatives in a time-dependent manner. Addition of adenine, cytidine or uridine nucleotide has no effects on the process. In contrast, guanine nucleotide triphosphates were stimulatory in a dose-dependent manner. The non-hydrolyzable derivative guanosine 5'-[γ-thio]triphosphate was the most effective activator while guanosine 5'[β-thio]diphosphate inhibited the action of GTP. It is suggested that GTP-binding proteins exist in the Acer membrane and play a regulatory role in the formation of potentially important second messengers