抄録
An occurrence of phosphatidylinositol 4, 5-bisphosphate (PIP2) phosphomonoesterase in human platelets was demonstrated by analyzing phosphoinositides metabolism. The activity of the enzyme was maximum at pH7.0. It was active even in the absence of Ca2+ or Mg2+ but it was enhanced in the presence of Mg2+ or NaF. The activity was inhibited by pyrophosphate. The activity was not altered in the presence of Ca2+ Thereby, besides phosphodiesteric cleavage by phospholipase C, the amount of PIP2 in activated platelets may be reduced by the combined effect of PIP2-phosphomonoesterase and suppressed activity of PI-kinase by Ca2+.
