Biosynthesis of paf‐acether XVII. Regulation by the CoA‐independent transacylase in human neutrophils

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Abstract
Treatment of intact human polymorphonuclear neutrophils (PMN) with low concentrations of phorbol myristate acetate (PMA, 1–10 ng/ml) induced paf-acether (pat) and lyso paf formation, arachidonate release, and simultaneous inhibition of CoA-independent lyso paf : transacylase as assayed in a cell-free system. Inhibition of [3H]lyso paf reacylation was also observed when it was exogenously added to the PMA-treated intact PMN. When higher concentrations of PMA (40–100 ng/ml) were used, paf biosynthesis was severely impaired and the level of the CoA-independent transacylase activity returned to basal level. Since lyso paf appears to be the substrate for PMA-activated paf formation (remodeling pathway), we showed that [14C]acetate was incorporated into the paf molecule. By contrast, labeling with [3H]choline was not appropriate in this model. The presented results are against the involvement of a de novo route in paf synthesis initiated by PMA and open a new possibility of an important role for the CoA-independent transacylase in controling the level of lyso paf availability for paf formation.