Nixon A B, Greene D G, Wykle R L
Department of Biochemistry, Bowman Gray School of Medicine, Winston-Salem, NC 27157-1016, USA.
Biochim Biophys Acta. 1996 May 20;1300(3):187-96. doi: 10.1016/0005-2760(96)00011-2.
In human neutrophils (PMN) the ethanolamine-containing phosphoglyceride fraction (PE), principally plasmalogen-linked PE (1-O-alk-1'-enyl-2-acyl-sn-glycero-3-phosphoethanolamine), is the major store of arachidonic acid (AA). Exogenous AA is initially incorporated into 1-acyl-linked phosphoglycerides and is believed to be transferred into the 1-ether-linked phosphoglycerides via the action of a CoA-independent transacylase (CoA-IT). We have investigated the selectivity for both the "acceptor' lysophospholipids and "donor' AA-containing phospholipid substrates in the CoA-IT reaction. Evidence suggests CoA-IT may also participate in the synthesis of platelet activating factor. The transfer of [3H]AA from endogenously labeled choline-containing phosphoglycerides (PC) to exogenously added alkenyl-lyso-PE (0-50 microM) was examined in saponin-permeabilized PMN. In these "donor' studies, we observed that [3H]AA was transferred from both alkyl- and diacyl-linked PC in a proportional manner. More detailed molecular species analysis showed that [3H]AA was deacylated from all the major AA-containing molecular species in both the alkyl and diacyl subclasses with no selectivity for either subclass. To investigate the "acceptor' selectivity, membrane fractions prelabeled with either [3H]alkyl-arachidonoyl-PE or -PC were utilized as donor substrates. Various unlabeled lysophospholipids (10 microM) were added and the generation of [3H]lyso-PE or -PC was monitored as a measure of CoA-IT activity. Significant subclass preference was observed upon addition of lyso-PE species (1-alkenyl > 1-alkyl > 1-acyl) however, little selectivity was seen with the corresponding lyso-PC species. On the other hand, lysophosphatidylserine, lysophosphatidylinositol, and lysophosphatidic acid all served as poor acceptor substrates in the reaction. These data from PMN are consistent with other evidence that the CoA-IT plays a pivotal role in the enrichment of AA into plasmalogen-linked PE.
在人类中性粒细胞（PMN）中，含乙醇胺的磷酸甘油酯部分（PE），主要是缩醛磷脂连接的PE（1-O-烷-1'-烯基-2-酰基-sn-甘油-3-磷酸乙醇胺），是花生四烯酸（AA）的主要储存形式。外源性AA最初掺入1-酰基连接的磷酸甘油酯中，并被认为通过一种不依赖辅酶A的转酰基酶（CoA-IT）的作用转移到1-醚连接的磷酸甘油酯中。我们研究了CoA-IT反应中对“受体”溶血磷脂和“供体”含AA磷脂底物的选择性。有证据表明CoA-IT也可能参与血小板活化因子的合成。在皂素通透的PMN中检测了[3H]AA从内源性标记的含胆碱磷酸甘油酯（PC）向外源性添加的烯基溶血PE（0 - 50 microM）的转移。在这些“供体”研究中，我们观察到[3H]AA以成比例的方式从烷基连接和二酰基连接的PC中转移出来。更详细的分子种类分析表明，[3H]AA从烷基和二酰基亚类中所有主要的含AA分子种类中脱酰化，对任何一个亚类都没有选择性。为了研究“受体”选择性，用[3H]烷基花生四烯酰-PE或-PC预标记的膜部分用作供体底物。加入各种未标记的溶血磷脂（10 microM），并监测[3H]溶血PE或-PC的生成作为CoA-IT活性测定。加入溶血PE种类时观察到显著的亚类偏好（1-烯基>1-烷基>1-酰基），然而，相应的溶血PC种类几乎没有选择性。另一方面，溶血磷脂酰丝氨酸、溶血磷脂酰肌醇和溶血磷脂酸在反应中都是较差的受体底物。来自PMN的这些数据与其他证据一致表明，CoA-IT在将AA富集到缩醛磷脂连接的PE中起关键作用。
