Three distinct lipid kinase activities are present in spinach chloroplast envelope membranes: Phosphatidylinositol phosphorylation is sensitive to wortmannin and not dependent on chloroplast ATP

Chloroplast envelope membranes display properties that are important in lip id synthesis, regulation of metabolites, and protein transport, as well as in signal transduction. The recent discovery showing that phosphorylation o f lipids occurs in envelope membranes provides a new approach for understan ding the role of chloroplast lipids in these processes. The present investi gation shows that three major lipid kinase activities are at least present in envelope membranes. These activities greatly depend on external conditio ns, such as pH, ATP concentrations, temperature, and chloroplast ATP and wo rtmannin sensitivity. Two types of phosphorylated lipid couples displayed s imilar intrinsic responses toward these biochemical parameters, namely phos phatidic acid (PA) and its lysoderivative (LPA) and monogalactosyl-phosphat e-diacylglyceroI (MGpDG) and its lysoderivative (LMGpDG), but not phosphati dyl-inositol-monophosphate (PIP) and its lysoderivative (LPIP). Phosphoryla tion of phosphatidylinositol. was not dependent on chloroplast ATP, but was sensitive toward wortmannin in intact chloroplasts and outer envelope memb rane vesicles. (C) 2001 Academic Press.