Acylation of 1-palmitoyl-sn-glycerophosphocholine by chick brain microsomes is unaffected by fatty acid binding protein.

Rates of incorporation of exogenously supplied fatty acids into 1-palmitoyl-sn-glycerophosphocholine were measured using the microsomal fraction from brains of 14-15 day old chick embryos. The substrate preferences for reacylation were: 18: 2(n-6) = 20: 4(n-6) > or = 20: 5(n-3) = 18: 3(n-3) > or = 18: 1(n-9) > or = 22: 6(n-3) > or = 18: 0. The normalized rate with 18: 0 was significantly lower than all other rates except for 22: 6(n-3), and the acylation rate with 22: 6(n-3) was significantly lower than with 18: 2(n-6) and 20: 5(n-3). With the addition of fatty acid binding protein partially purified from brain cytosol, a decrease (not significant) in the rate of incorporation was observed; the substrate preference was unchanged. In the presence of FABP, normalized rates with 18: 2(n-6) were significantly higher than with 18: 0, 18: 1(n-9), or 22: 6(n-3); rates with 20: 4(n-6) were significantly higher than those with 22: 6(n-3). Preliminary data on the acylation of 1-palmitoyl-sn-glycerophosphoethanolamine showed lower rates of incorporation than for the choline analogue and no clear substrate preference, but a similar lack of effect of fatty acid binding protein. These results do not support the proposed function of fatty acid binding protein in the establishment of a phospholipid composition rich in polyunsaturated fatty acids. The results are consistent, however, with the role of the reacylation reaction in the continual turnover of particular substrates [18: 2(n-6) and 20: 4(n-6)] used to generate second messengers.