Castagnet P I, Giusto N M
Instituto de Investigaciones Bioquímicas, Universidad Nacional del Sur y Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina.
Arch Biochem Biophys. 1997 Apr 1;340(1):124-34. doi: 10.1006/abbi.1996.9876.
In the present paper the properties of acyl-CoA:lysophosphatidylcholine acyltransferase activity associated with rod outer segments (ROS) have been studied. Under adequate experimental conditions, ROS acyl-CoA:lysophosphatidylcholine acyltransferase activity presented a maximum at pH 7.0. The enzyme was able to incorporate as much as 60% of the label offered as [1-14C]oleoyl-CoA into phosphatidylcholine after 5 min of incubation. The use of varying concentrations of oleoyl-CoA and 46 microM lysophosphatidylcholine gave an apparent K(m) value for oleoyl-CoA of 100 microM and a Vmax value of 153 nmol x h-1 x (mg protein)-1. The use of varying concentrations of lysophosphatidylcholine and 100 microM oleoyl-CoA gave an apparent K(m) value for lysophosphatidylcholine of 27 microM and a Vmax value of 155 nmol x h-1 x (mg protein)-1. The enzyme was inhibited by 25% when ROS membranes were incubated in the presence of 10 mM MgCl2. The acyltransferase was able to incorporate other acyl-CoAs (palmitoyl-CoA and arachidonoyl-CoA) into ROS phospholipids and to acylate other lysophospholipids but less efficiently than lysophosphatidylcholine. Lysophoshatidylcholine was preferentially acylated with arachidonic acid followed by oleic acid and, less efficiently, with palmitic acid. The high specific activity of acyl-CoA lysophosphatidylcholine acyltransferase found in purified ROS compared to the activity found in other subcellular fractions of the bovine retina suggests that this enzymatic activity is native to the ROS.
在本论文中，对与视杆细胞外段（ROS）相关的酰基辅酶A：溶血磷脂酰胆碱酰基转移酶活性的特性进行了研究。在适当的实验条件下，ROS酰基辅酶A：溶血磷脂酰胆碱酰基转移酶活性在pH 7.0时呈现最大值。孵育5分钟后，该酶能够将高达60%的以[1-14C]油酰辅酶A形式提供的标记物掺入磷脂酰胆碱中。使用不同浓度的油酰辅酶A和46微摩尔的溶血磷脂酰胆碱，得出油酰辅酶A的表观K(m)值为100微摩尔，Vmax值为153纳摩尔·小时-1·（毫克蛋白质）-1。使用不同浓度的溶血磷脂酰胆碱和100微摩尔的油酰辅酶A，得出溶血磷脂酰胆碱的表观K(m)值为27微摩尔，Vmax值为155纳摩尔·小时-1·（毫克蛋白质）-1。当ROS膜在10毫摩尔氯化镁存在下孵育时，该酶活性被抑制25%。酰基转移酶能够将其他酰基辅酶A（棕榈酰辅酶A和花生四烯酰辅酶A）掺入ROS磷脂中，并使其他溶血磷脂酰化，但效率低于溶血磷脂酰胆碱。溶血磷脂酰胆碱优先被花生四烯酸酰化，其次是油酸，被棕榈酸酰化的效率较低。与牛视网膜其他亚细胞组分中的活性相比，在纯化的ROS中发现的酰基辅酶A溶血磷脂酰胆碱酰基转移酶的高比活性表明这种酶活性是ROS所特有的。
