Properties of PAF-synthesizing phosphocholinetransferase and evidence for lysoPAF acetyltransferase activity in rat brain |
| |
Authors: | Gianfrancesco Goracci Ermelinda Francescangeli |
| |
Affiliation: | (1) Dipartimento di Medicina Sperimentale e Scienze Biochemiche, Università di Perugia, Via del Giochetto, 06100 Perugia, Italy |
| |
Abstract: | Several reports have indicated that platelet-activating factor (PAF) may play a role in the physiopathology of nervous tissue.
We previously have demonstrated the presence, in the microsomal fractions of rat brain, of a phosphocholinetransferase which
is able to synthesize PAF by thede novo pathway. The presence of dithiothreitol in the medium increases the rate of PAF biosynthesis, whereas it inhibits the synthesis
of long-chain alkylacyl- and diacyl-glycerophosphocholines (GPC), including dioctanoyl-GPC. This and other properties, such
as pH dependence and thermal stability, indicate that rat brain may have two distinct enzymes for the synthesis of PAF and
other choline phospholipids. The affinity of these enzymes for CDPcholine is similar to that reported for other tissues, the
Km being 42 μm and 55 μm with alkylacetylglycerol and dioctanoylglycerol as lipid substrates, respectively. The Vmax values were 3.0 and 2.2 nmol/mg prot/min for PAF and dioctanoyl-GPC, respectively. In addition, it was shown that the microsomal
fraction of rat brain contains an acetyltransferase which can convert lysoPAF to PAF. Since it has been reported previously
that brain tissue possesses phospholipase A2 activity that can hydrolyze alkylacyl-GPC to lysoPAF, we conclude that brain tissue has all enzymic activities for the synthesis
of PAF by the “remodeling pathway”. The role of the two routes of PAF biosynthesis in nervous tissue remains to be established.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, Tokyo, Japan, May 1989. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|