Mitranic M M, Boggs J M, Moscarello M A
Biochim Biophys Acta. 1982 Dec 8;693(1):75-84. doi: 10.1016/0005-2736(82)90472-2.
The effects of the membrane perturbing reagents linoleic acid and benzyl alcohol on the activities of four rat liver Golgi membrane enzymes, N-acetylglucosaminyl-, N-acetylgalactosaminyl-, galactosyl-, and sialyltransferases and several soluble glycosyltransferases, bovine milk galactosyl- and N-acetylglucosaminyltransferases and porcine submaxillary N-acetylgalactosaminyltransferases have been studied. In rat liver Golgi membranes, linoleic acid inhibited the activities of N-acetylgalactosaminyl- and galactosyltransferases by 50% or greater, sialyltransferase by 10-15%, and N-acetylglucosaminyltransferase not at all. The isolated bovine milk N-acetylglucosaminyltransferase and porcine submaxillary N-acetylgalactosylaminyltransferase were not inhibited but bovine milk galactosyltransferase was inhibited by 95% or greater. The inhibition by linoleic acid on Golgi membrane galactosyltransferase appears to be a direct effect of the reagent on the enzyme. Incorporation of bovine milk galactosyltransferase into liposomes formed from saturated phospholipids, DMPC, DPPC, and DSPC (dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholine) prevented inhibition of the enzyme activity suggesting that the lipid formed a barrier which did not allow linoleic acid access to the enzyme. The water soluble benzyl alcohol was more effective in inhibiting enzymes of the isolated rat liver Golgi complex. All four glycosyltransferases were inhibited, the N-acetylglucosaminyl- and N-acetylgalactosaminyltransferases by more than 95%. A higher concentration of benzyl alcohol was necessary to inhibit the galactosyltransferases than was required for the other Golgi enzymes. Benzyl alcohol also inhibited the isolated bovine milk N-acetylglucosaminyl- and galactosyltransferases 90% to 95%, respectively, but did not affect the isolated porcine submaxillary gland N-acetylgalactosaminyltransferase. Benzyl alcohol did not inhibit the milk galactosyltransferase incorporated into DMPC or DPPC liposomes but showed a complex effect on the activity of the enzyme incorporated into DSPC vesicles, a stimulation of activity at low concentrations followed by an inhibition. A lipid environment consisting of saturated lipids appears to present a barrier to inhibiting substances such as linoleic acid and benzyl alcohol, or lipid may stabilize the active conformation of the enzyme. The different effects of these reagents on four transferases of the Golgi complex suggest that the lipid environment around these enzymes may be different for each transferase.
已研究了膜扰动试剂亚油酸和苯甲醇对四种大鼠肝脏高尔基体膜酶（N - 乙酰葡糖胺基转移酶、N - 乙酰半乳糖胺基转移酶、半乳糖基转移酶和唾液酸转移酶）以及几种可溶性糖基转移酶（牛乳半乳糖基转移酶和N - 乙酰葡糖胺基转移酶、猪颌下腺N - 乙酰半乳糖胺基转移酶）活性的影响。在大鼠肝脏高尔基体膜中，亚油酸使N - 乙酰半乳糖胺基转移酶和半乳糖基转移酶的活性抑制达50%或更高，唾液酸转移酶活性抑制10 - 15%，而对N - 乙酰葡糖胺基转移酶活性完全没有抑制作用。分离出的牛乳N - 乙酰葡糖胺基转移酶和猪颌下腺N - 乙酰半乳糖胺基转移酶未受抑制，但牛乳半乳糖基转移酶活性抑制达95%或更高。亚油酸对高尔基体膜半乳糖基转移酶的抑制作用似乎是该试剂对酶的直接作用。将牛乳半乳糖基转移酶掺入由饱和磷脂（二肉豆蔻酰磷脂酰胆碱、二棕榈酰磷脂酰胆碱和二硬脂酰磷脂酰胆碱）形成的脂质体中可防止酶活性受到抑制，这表明脂质形成了一道屏障，使亚油酸无法接触到酶。水溶性苯甲醇对分离出的大鼠肝脏高尔基体复合物中的酶具有更强的抑制作用。所有四种糖基转移酶均受到抑制，N - 乙酰葡糖胺基转移酶和N - 乙酰半乳糖胺基转移酶的抑制率超过95%。抑制半乳糖基转移酶所需的苯甲醇浓度高于其他高尔基体酶。苯甲醇还分别使分离出的牛乳N - 乙酰葡糖胺基转移酶和半乳糖基转移酶活性抑制90%至95%，但对分离出的猪颌下腺N - 乙酰半乳糖胺基转移酶没有影响。苯甲醇不会抑制掺入二肉豆蔻酰磷脂酰胆碱或二棕榈酰磷脂酰胆碱脂质体中的牛乳半乳糖基转移酶，但对掺入二硬脂酰磷脂酰胆碱囊泡中的该酶活性表现出复杂的影响，低浓度时刺激活性，随后抑制活性。由饱和脂质组成的脂质环境似乎对亚油酸和苯甲醇等抑制性物质形成了一道屏障，或者脂质可能稳定了酶的活性构象。这些试剂对高尔基体复合物中四种转移酶的不同影响表明，这些酶周围的脂质环境可能因每种转移酶而异。
