A simple and inexpensive method for the preparation of (beta,gamma-32P) guanosine 5'-triphosphate.

A rapid and inexpensive method has been developed for the synthesis of 32P-labeled guanosine 5'-triphosphate (GTP). When yolk platelets isolated from brine shrimp cysts are incubated with 32PPi at pH 5.8 and in the presence of 10 mM MgCl2 and 5 mM dithiothreitol, the primary compound formed is [beta,gamma-32P]GTP. The synthetic reaction is catalyzed by the yolk platelet enzyme, GTP : GTP guanylyltransferase, which has been demonstrated to be important in the biosynthesis of diguanosine 5'-tetraphosphate (Gp4G), the major purine nucleotide in brine shrimp yolk platelets and encysted embryos.