Vunnam R R, Radin N S
Biochim Biophys Acta. 1979 Apr 27;573(1):73-82. doi: 10.1016/0005-2760(79)90174-7.
In order to increase the sensitivity of the assay for ceramide: UDPGlc glucosyltransferase, the enzyme that makes glucocerebroside, we synthesized a variety of ceramide homologues that might be better substrates than the naturally occurring ceramides. N-Octanoyl sphingosine proved to be the best lipid tested in liver and brain. It could be added to the tissue homogenate in the dry form, as a thin layer coated on Celite, or in liposomes, prepared from lecithin and cerebroside sulfate. The liposomal form produced better replication of assay values. It is suggested that the addition of cerebroside sulfate to liposomal preparations might be a good, and more physiological, replacement for the commonly used dicetyl phosphate. A new homologue of DL-sphinganine, decasphinganine, was synthesized by an efficient series of steps and acylated with different fatty acids to form ceramide homologues. The best substrate in this series was the lauroyl amide and it is suggested that this lipid be used in cerebroside synthetase assays because of the convenience of preparing it, even though it is not as good as octanoyl sphingosine. Both compounds are distinctly better than natural ceramide or DL-sphinganine amides. From comparisons of enzyme activity under various conditions, the tentative conclusion is drawn that the enzymes in liver and brain have different properties, and that liver has two different synthetases.
UDPGlc葡糖基转移酶（即生成葡糖脑苷脂的酶）检测的灵敏度，我们合成了多种神经酰胺同系物，它们可能比天然存在的神经酰胺更适合作为底物。N-辛酰鞘氨醇被证明是在肝脏和大脑中测试的最佳脂质。它可以以干燥形式添加到组织匀浆中，如涂覆在硅藻土上的薄层，或者以由卵磷脂和硫酸脑苷脂制备的脂质体形式添加。脂质体形式产生了更好的检测值重复性。有人建议，向脂质体制剂中添加硫酸脑苷脂可能是一种很好的、更符合生理的替代常用的磷酸二鲸蜡酯的物质。通过一系列高效步骤合成了一种新的DL-鞘氨醇同系物——十鞘氨醇，并将其用不同脂肪酸酰化以形成神经酰胺同系物。该系列中最佳的底物是月桂酰酰胺，尽管它不如辛酰鞘氨醇，但由于其制备方便，建议将这种脂质用于脑苷脂合成酶检测。这两种化合物都明显优于天然神经酰胺或DL-鞘氨醇酰胺。通过在各种条件下对酶活性的比较，初步得出结论：肝脏和大脑中的酶具有不同的特性，并且肝脏中有两种不同的合成酶。
