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

Membranes 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.