Replacement of ethanolamine phosphate by 3-aminopropylphosphonate in the phospholipids of Tetrahymena

When Tetrahymena thermophila is grown on a medium containing up to 5 mm 3-aminopropylphosphonate, up to 90% of the ethanolamine phosphate in phosphatidylethanolamine is replaced by the 3-aminopropylphosphonate. No accompanying alteration of the phospholipid composition of Tetrahymena is observed. This contrasts with the results obtained when 2-aminoethylphosphonate, the naturally occurring compound, is added to the growth medium (Biochim. Biophys. Acta528, 394–398, 1978); the 2-aminoethylphosphonate causes a substantial increase in the 2-aminoethylphosphonolipid and a reciprocal decrease in phosphatidylethanolamine. Thus, there is apparently a one-way control system in Tetrahymena whereby 2-aminoethylphosphonate and its phosphonolipid may influence the level of phosphatidylethanolamine in the cell, but ethanolamine phosphate, as represented by its isosteric analog, does not influence the phospholipid levels. There is no effect of the 3-aminopropylphosphonate on de novo 2-aminoethylphosphonate biosynthesis indicating a strict specificity for 2-aminoethylphosphonate as its own feedback inhibitor.