Pak Y, Joó F, Vigh L, Katho A, Thompson G A
Department of Botany, University of Texas, Austin 78713.
Biochim Biophys Acta. 1990 Apr 13;1023(2):230-8. doi: 10.1016/0005-2736(90)90418-n.
Various conditions were tested in an attempt to hydrogenate the unsaturated fatty acids of living Tetrahymena mimbres with the homogeneous catalyst palladium di-(sodium alizarine monosulfonate) without causing serious damage to the cells. Using a low (20 micrograms/ml) catalyst concentration in the external medium, hydrogenation of greater than 20% of surface membrane lipid double bonds were obtained, but hydrogenation of intracellular membranes was minimal. When exposed to H2, cells preincubated with inactive catalyst for several hours and visibly loaded with the catalyst lost viability as soon as hydrogenation exceeded trace levels. Material secreted by Tetrahymena into their medium effectively inhibited hydrogenation of added oleic acid, normally a good substrate. Mucus secreted by the cells, soluble proteins isolated from cell homogenates, bovine serum albumin, and cysteine were also inhibitory, but the inhibition could be overcome by employing higher catalyst concentrations. Although some enzymatic retroconversion of saturated lipids back to unsaturated lipids appeared to take place, the scale of the conversion was small, and further experimentation will be required to understand the mechanism involved. The selective hydrogenation of surface membranes achieved by these methods may be especially useful to those interested in fluidity effects on plasma membrane properties.
为了用均相催化剂二（茜素单磺酸钠）钯氢化活的米氏四膜虫的不饱和脂肪酸，同时又不严重损害细胞，对各种条件进行了测试。在外部培养基中使用低浓度（20微克/毫升）的催化剂，可使超过20%的表面膜脂质双键氢化，但细胞内膜的氢化程度极小。当暴露于氢气中时，预先用无活性催化剂孵育数小时且明显负载有催化剂的细胞，一旦氢化超过微量水平，就会失去活力。四膜虫分泌到培养基中的物质能有效抑制添加的油酸（通常是良好的底物）的氢化。细胞分泌的黏液、从细胞匀浆中分离出的可溶性蛋白质、牛血清白蛋白和半胱氨酸也具有抑制作用，但通过采用更高的催化剂浓度可以克服这种抑制。尽管似乎发生了一些饱和脂质酶促逆转为不饱和脂质的过程，但转化规模较小，需要进一步实验来了解其中涉及的机制。通过这些方法实现的表面膜选择性氢化，对于那些对流动性对质膜性质的影响感兴趣的人可能特别有用。
