PHOSPHOINOSITIDE HYDROLYSIS BY PHOSPHOLIPASE-C MODULATED BY MULTIVALENT CATIONS LA3+, AL3+, NEOMYCIN, POLYAMINES, AND MELITTIN

Second messenger production from phosphoinositide hydrolysis is regula ted by different pathways, such as G-proteins or tyrosine phosphorylat ion of phosphoinositide phospholipase C (PI-PLC). Another means of alt ering the activity of PI-PLC is through cation interaction with the ph osphoinositide substrate. A variety of organic and inorganic multi-val ent cations were examined for their effects on the activity of purifie d PI-PLC delta. Surprisingly, the cations produced both stimulation an d inhibition of PI-PLC catalyzed phosphoinositide hydrolysis, dependin g on the substrate and the ion to phosphoinositide stoichiometry. Thes e data support the hypothesis that ionic complexes with phosphoinositi des may alter their hydrolysis by PI-PLC.