A thiophosphate analog of dimyristoylphosphatidyl-inositol-4-phosphate is a substrate for mammalian phosphoinositide-specific phospholipase c

1,2-Dimyristoyloxypropane-3-thiophosphate(rac-1-myo-inositol-4-phosphate), a thiophosphate analog of dimyristoyl phosphatidylinositol-4-phosphate was synthesized as a substrate for mammalian phosphoinositide-specific phospholipase C. Its activity with Δ(1–132)-PI-PLC-δ1 (a deletion mutant with the N-terminal pleckstrin homology domain removed) was studied in sonicated dispersions, with and without added Triton X-100. It had an initial activity of about 30 μmol min−1 mg−1, which rapidly decreased due to substrate depletion in the vesicle or micelle. The slower rate of hydrolysis appeared limited by enzyme hopping or exchange of substrate between vesicles or micelles, which was more rapid in the presence of detergent.