Chaudhary L R, Nelson E C
Biochim Biophys Acta. 1987 Jan 13;917(1):24-32. doi: 10.1016/0005-2760(87)90279-7.
The present study was conducted to examine esterification of retinol by testicular microsomes. The microsomes were isolated from rat testes and were incubated under varying assay conditions with [3H]retinol. [3H]Retinylpalmitate was identified by reversed-phase high-performance liquid chromatography as an esterified product. The rate of esterification was increased by the addition of a fatty acyl-CoA. Coenzyme A esters of oleic, palmitic and stearic acids were equally effective substrates for retinol esterification. A 17-fold increase was observed in the presence of palmitoyl-CoA when microsomes had been pretreated with hydroxylamine, a reagent that reacts with coenzyme A thioesters to form hydroxamic acids. The esterifying activity was stimulated by the addition of dithiothreitol (4 mM) and fatty acid-free bovine serum albumin (1 mg/ml). The optimal concentrations for retinol and palmitoyl-CoA were 40 microM and 30-40 microM, respectively. The enzyme activity was inhibited by p-hydroxymercuribenzoate, sodium taurocholate and 5,5'-dithiobis-(2-nitrobenzoic acid), but not by EDTA. The enzyme activity was highest in microsomes (36%). However, some activity was present in mitochondria (29%). These results clearly show the presence of a fatty acyl-CoA: retinol acyltransferase that catalyzes the esterification of retinol in rat testes.
本研究旨在检测睾丸微粒体对视黄醇的酯化作用。从大鼠睾丸中分离出微粒体，并在不同的测定条件下与[3H]视黄醇一起孵育。通过反相高效液相色谱法鉴定出[3H]视黄醇棕榈酸酯为酯化产物。添加脂肪酰辅酶A可提高酯化速率。油酸、棕榈酸和硬脂酸的辅酶A酯对视黄醇酯化是同样有效的底物。当微粒体用羟胺预处理时，在棕榈酰辅酶A存在下观察到酯化活性增加了17倍，羟胺是一种与辅酶A硫酯反应形成异羟肟酸的试剂。添加二硫苏糖醇（4 mM）和无脂肪酸牛血清白蛋白（1 mg/ml）可刺激酯化活性。视黄醇和棕榈酰辅酶A的最佳浓度分别为40 microM和30 - 40 microM。对羟基汞苯甲酸、牛磺胆酸钠和5,5'-二硫代双（2-硝基苯甲酸）可抑制酶活性，但EDTA无此作用。酶活性在微粒体中最高（36%）。然而，线粒体中也存在一些活性（29%）。这些结果清楚地表明大鼠睾丸中存在一种脂肪酰辅酶A：视黄醇酰基转移酶，它催化视黄醇的酯化反应。
