Pitto M, Palestini P, Masserini M
Department of Medical Chemistry and Biochemistry, University of Milan, Italy.
FEBS Lett. 1996 Apr 1;383(3):223-6. doi: 10.1016/0014-5793(96)00262-1.
The dependence of CMP-N-acetylneuraminate:GM1 sialyltransferase (SAT IV) activity of rat liver Golgi apparatus on GM1 ganglioside ceramide composition was evaluated. SAT IV activity was assayed on GM1 molecular species carrying homogeneous ceramide moieties containing long chain bases of different length (18 or 20 C atoms) unsaturated or not, linked to 14:0, 16:0, 18:0 or 22:0 fatty acids. The results obtained in the presence of the detergent Triton CF-54, when enzyme and substrate are presumably part of the same supramolecular structure, show that either the long chain base or the fatty acid composition can affect enzyme activity. This feature was not displayed when GM1 was embedded in dipalmitoylphosphatidylcholine vesicles in the absence of detergent. Under the latter conditions, the enzyme was not sensitive to the lipid composition of GM1 but to the ganglioside/phospholipid ratio in the vesicles. These results indicate for the first time that SAT IV is affected by the lipid composition of the substrate and strengthen the hypothesis that glycosyltranferases may contribute to control the cellular glycosphingolipid ceramide pattern.
评估了大鼠肝脏高尔基体中CMP-N-乙酰神经氨酸：GM1唾液酸转移酶（SAT IV）活性对GM1神经节苷脂神经酰胺组成的依赖性。在携带均一神经酰胺部分的GM1分子种类上测定SAT IV活性，这些神经酰胺部分含有不同长度（18或20个碳原子）的不饱和或饱和长链碱基，与14:0、16:0、18:0或22:0脂肪酸相连。当酶和底物可能是同一超分子结构的一部分时，在去污剂Triton CF-54存在下获得的结果表明，长链碱基或脂肪酸组成均可影响酶活性。当GM1在无去污剂的情况下包埋于二棕榈酰磷脂酰胆碱囊泡中时，未显示出此特征。在后一种条件下，该酶对GM1的脂质组成不敏感，而是对囊泡中的神经节苷脂/磷脂比例敏感。这些结果首次表明SAT IV受底物脂质组成的影响，并强化了糖基转移酶可能有助于控制细胞糖鞘脂神经酰胺模式的假说。
