Palmitoyl transferase activity of lecithin retinol acyl transferase
Palmitoyl transferase activity of lecithin retinol acyl transferase
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DOI：
10.1021/bi060897y
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发表时间：
2006-09-05
期刊：
影响因子：
2.9
通讯作者：
Rando, Robert R.
中科院分区：
文献类型：
--
作者：
Xue, Linlong;Jahng, Wan Jin;Rando, Robert R.
卵磷脂视黄醇酰基转移酶(LRAT)催化卵磷脂sn-1位的酰基转移到维生素A上，生成全反式视黄酸酯(Tres)。此前的体外研究表明，LRAT还可以在RPE65和TRES之间交换棕榈酰基。RPE65是一种对视觉至关重要的TrE结合蛋白。这种交换很可能在视觉周期的运行中具有监管意义。在本研究中，以棕榈酰化氨基酸和二肽作为RPE65的替代物，探讨了LRAT的底物特异性。O-取代和S取代的棕榈酰化类似物都是tLRAT的良好底物，tLRAT是一种易于表达和纯化的LRAT形式。使用维生素A作为棕榈酰基受体，很容易形成Tres。这些反应的同源物也发生在粗大的视网膜色素上皮(RPE)膜上。含LRAT的RPE膜将标记的[1-C-14]-(L)-α-二棕榈酰二磷脂酰胆碱(DP*PC)转移到RPE65上。在膜中和纯化的tLRAT预先孵育一种特定的LRAT拮抗剂可以取消棕榈酰基转移。这些实验与LRAT作为一种蛋白质棕榈酰基转移酶功能的扩展作用是一致的。
Lecithin retinol acyl transferase (LRAT) has the essential role of catalyzing the transfer of an acyl group from the sn-1 position of lecithin to vitamin A to generate all-trans-retinyl esters (tREs). In vitro studies had shown previously that LRAT also can exchange palmitoyl groups between RPE65, a tRE binding protein essential for vision, and tREs. This exchange is likely to be of regulatory significance in the operation of the visual cycle. In the current study, the substrate specificity of LRAT is explored with palmitoylated amino acids and dipeptides as RPE65 surrogates. Both O- and S-substituted palmitoylated analogues are excellent substrates for tLRAT, a readily expressed and readily purified form of LRAT. Using vitamin A as the palmitoyl acceptor, tREs are readily formed. The cognate of these reactions occurs in crude retinal pigment epithelial (RPE) membranes as well. RPE membranes containing LRAT transfer palmitoyl groups from radiolabeled [1-C-14]-(L)-alpha-dipalmitoyl diphosphatidylcholine (DP*PC) to RPE65. Palmitoyl transfer is abolished by preincubation with a specific LRAT antagonist both in membranes and with purified tLRAT. These experiments are consistent with an expanded role for LRAT function as a protein palmitoyl transferase.