In:
European Journal of Biochemistry, Wiley, Vol. 216, No. 3 ( 1993-09), p. 835-840
Abstract:
We have recently demonstrated that arachidonate [20:4(5,8,11,14)] was primarily linked to the hexadecyl (16:0) and octadecenyl (18:1) species of alkylacyl derivatives of glycerolphosphocholine (Gro P Cho). Consistent with the involvement of arachidonate‐specific CoA‐independent transacylase in the synthesis of platelet‐activating factor (PAF: 1‐ O ‐alkyl‐2‐acetyl‐Gro P Cho), 16:0 and 18:1 PAF species were formed upon antigen stimulation [Joly, F., Breton, M., Wolf, C., Ninio, E. & Colard, O. (1992) Biochim. Biophys. Acta 1125 , 305–312]. In the present work, addition of lyso‐PAF to m ast cells resulted in PAF production. We analyzed the PAF species formed in the presence of a defined lyso‐PAF molecular species in order to differentiate between either direct acetylation or involvement of the membrane precursor. The 18:1 lyso‐PAF was more effective than the 16:0 in producing PAF which was composed of 95% 18:1 PAF, the balance being 16:0, indicating that part of the acetylated lyso‐PAF originated from the cellular pool of alkyl‐arachidonyl‐Gro P Cho in resting cells. Consistent with alkyl‐arachidonyl‐Gro P Cho species content and acetyltransferase specificity, similar amounts of 16:0 and 18:1 PAF species were formed when mast cells were stimulated with antigen. Supplemented with 16:0 or 18:1 lyso‐PAF, antigen‐stimulated mast cells responded by 230% and 125% increase in PAF synthesis, respectively. As expected, the amount of the PAF species corresponding to the added lyso‐PAF was increased. More interestingly, addition of 16:0 lyso‐PAF almost doubled the amount of 18:1 PAF content as compared to antigen alone, thus indicating that the lyso‐PAF formed via the CoA‐independent transacylase was significantly used for PAF synthesis. despite a large excess of exogenous lyso‐PAF. The CoA‐independent transacylase, measured using [ 3 H]lyso‐PAF as a substrate in sonicates from antigen‐stimulated cells, was decreased concurrently with PAF formation. In conclusion, we show that when lyso‐PAF is added to mast cells, a direct acetylation may occur. However, PAF is preferentially synthesized through a mechanism involving the CoA‐independent transacylase reaction.
Type of Medium:
Online Resource
ISSN:
0014-2956
,
1432-1033
DOI:
10.1111/ejb.1993.216.issue-3
DOI:
10.1111/j.1432-1033.1993.tb18205.x
Language:
English
Publisher:
Wiley
Publication Date:
1993
detail.hit.zdb_id:
1398347-7
detail.hit.zdb_id:
2172518-4
SSG:
12
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