Role of carnitine and carnitine palmitoyltransferase as integral components of the pathway for membrane phospholipid fatty acid turnover in intact human erythrocytes.
Role of carnitine and carnitine palmitoyltransferase as integral components of the pathway for membrane phospholipid fatty acid turnover in intact human erythrocytes.
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DOI：
10.1016/s0021-9258(18)42330-7
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发表时间：
1992-06
期刊：
影响因子：
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通讯作者：
A. Arduini;G. Mancinelli;G. Radatti;S. Dottori;F. Molajoni;R. Ramsay
中科院分区：
文献类型：
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作者：
A. Arduini;G. Mancinelli;G. Radatti;S. Dottori;F. Molajoni;R. Ramsay
磷脂的脱酰化和再酰化过程是红细胞膜周转和修复的主要途径。在本文中，我们研究了肉碱棕榈酰转移酶在红细胞膜磷脂脂肪酸周转中的作用。酰基-L-肉碱作为活化酰基库的作用、肉碱的缓冲功能以及酰基-CoA/游离CoA比率在红细胞膜磷脂再酰化过程中的重要性也已得到解决。在完整的红细胞中，[1-14C]棕榈酸与酰基-L-肉碱、磷脂酰胆碱和磷脂酰乙醇胺的结合在至少3小时内与时间呈线性关系。最大比例的放射性存在于酰基-L-肉碱中。使用[1-14C]棕榈酸和[9,10-3H]油酸的竞争实验表明，[9,10-3H]油酸优先掺入磷脂中，较少掺入酰基-L-肉碱中。当红细胞悬浮液与[1-14C]棕榈酰-L-肉碱一起孵育时，在磷脂部分中回收了放射性标记的棕榈酸酯，并且肉碱棕榈酰转移酶抑制剂2-十四烷基缩水甘油酸完全消除了这种掺入。 ATP耗竭减少了[1-14C]棕榈酸和/或[9,10-3H]油酸与酰基-L-肉碱的结合，但与磷脂酰胆碱和磷脂酰乙醇胺的结合不受影响。相反，ATP消耗增强了[1-14C]棕榈酰-L-肉碱中放射性标记的脂肪酸与磷脂酰胆碱和磷脂酰乙醇胺的结合。这些数据表明存在酰基-L-肉碱库，与酰基-CoA库处于平衡状态，酰基-CoA库充当活化酰基的储存库。仅当完整红细胞与[9,10-3H]油酸一起孵育时，2-十四烷基缩水甘油酸或棕榈酰-D-肉碱对肉碱棕榈酰转移酶的抑制导致放射性标记脂肪酸掺入膜磷脂的显着减少。后面这些数据可以通过酰基辅酶A合成酶与棕榈酸酯和油酸酯的再酰化酶之间的速率和底物特异性的差异来解释，这支持肉碱棕榈酰转移酶在调节膜磷脂脂肪酸周转的生理表达的最佳酰基辅酶A/游离辅酶A比率方面的重要性。
The deacylation and reacylation process of phospholipids is the major pathway of turnover and repair in erythrocyte membranes. In this paper, we have investigated the role of carnitine palmitoyltransferase in erythrocyte membrane phospholipid fatty acid turnover. The role of acyl-L-carnitine as a reservoir of activated acyl groups, the buffer function of carnitine, and the importance of the acyl-CoA/free CoA ratio in the reacylation process of erythrocyte membrane phospholipids have also been addressed. In intact erythrocytes, the incorporation of [1-14C]palmitic acid into acyl-L-carnitine, phosphatidylcholine, and phosphatidylethanolamine was linear with time for at least 3 h. The greatest proportion of the radioactivity was found in acyl-L-carnitine. Competition experiments using [1-14C]palmitic and [9,10-3H]oleic acid demonstrated that [9,10-3H]oleic acid was incorporated preferentially into the phospholipids and less into acyl-L-carnitine. When an erythrocyte suspension was incubated with [1-14C]palmitoyl-L-carnitine, radiolabeled palmitate was recovered in the phospholipid fraction, and the carnitine palmitoyltransferase inhibitor, 2-tetradecylglycidic acid, completely abolished the incorporation. ATP depletion decreased incorporation of [1-14C]palmitic and/or [9,10-3H]oleic acid into acyl-L-carnitine, but the incorporation into phosphatidylcholine and phosphatidylethanolamine was unaffected. In contrast, ATP depletion enhanced the incorporation into phosphatidylcholine and phosphatidylethanolamine of the radiolabeled fatty acid from [1-14C]palmitoyl-L-carnitine. These data are suggestive of the existence of an acyl-L-carnitine pool, in equilibrium with the acyl-CoA pool, which serves as a reservoir of activated acyl groups. The carnitine palmitoyltransferase inhibition by 2-tetradecylglycidic acid or palmitoyl-D-carnitine caused a significant reduction of radiolabeled fatty acid incorporation into membrane phospholipids, only when intact erythrocytes were incubated with [9,10-3H]oleic acid. These latter data may be explained by the differences in rates and substrates specificities between acyl-CoA synthetase and the reacylating enzymes for palmitate and oleate, which support the importance of carnitine palmitoyltransferase in modulating the optimal acyl-CoA/free CoA ratio for the physiological expression of the membrane phospholipids fatty acid turnover.